feat: offline map download via MapLibre OfflineManager

New src/services/offline.ts:
- downloadRegion(): createPack with bounds, zoom 6-16, progress callback
- listRegions() / deleteRegion(): pack management
- expandBounds(): adds 5km buffer around the visible area
- formatBytes(): human-readable size string

RecordingScreen:
- MapRef attached to Map component to read getBounds()
- '↓ Offline' overlay button (Liberty style + idle state only)
- Modal: name input → download → progress bar with % and MB counter
- Raster styles show no download button (not supported by OfflineManager)

Settings → App → Offline maps:
- Lists all downloaded regions with size and tile count
- Delete with confirm alert
- Placeholder text when no regions exist

src/screens/RecordingScreen.tsx

@@ -1,23 +1,34 @@
 import React, { useEffect, useRef, useState, useMemo } from 'react';
-import { View, Text, StyleSheet, TouchableOpacity, Alert } from 'react-native';
+import { View, Text, StyleSheet, TouchableOpacity, Alert, Modal, TextInput, Pressable } from 'react-native';
 import { useNavigation } from '@react-navigation/native';
 import { NativeStackNavigationProp } from '@react-navigation/native-stack';
 import { activateKeepAwakeAsync, deactivateKeepAwake } from 'expo-keep-awake';
-import { Map, Camera, GeoJSONSource, Layer, UserLocation } from '@maplibre/maplibre-react-native';
+import { Map, Camera, GeoJSONSource, Layer, UserLocation, type MapRef } from '@maplibre/maplibre-react-native';
 import type { LineLayerStyle, CircleLayerStyle } from '@maplibre/maplibre-react-native';
+import { useSafeAreaInsets } from 'react-native-safe-area-context';
 import { useRecordingStore } from '../store/recording';
 import { startGpsRecording, stopGpsRecording, requestLocationPermissions, requestForegroundLocation } from '../services/gps';
 import { RootStackParamList } from '../types';
 import { colors } from '../theme';
 import { useTheme } from '../ThemeContext';
 import { MAP_STYLES } from '../mapStyles';
+import { downloadRegion, formatBytes, expandBounds, OFFLINE_STYLE_URL } from '../services/offline';
 
 type Nav = NativeStackNavigationProp<RootStackParamList>;
 
 export function RecordingScreen() {
   const nav = useNavigation<Nav>();
+  const insets = useSafeAreaInsets();
   const { accent, accentDim, scale, boldLabels, mapOrientation, mapTileStyle } = useTheme();
   const mapStyle = MAP_STYLES[mapTileStyle].style;
+  const mapRef = useRef<MapRef>(null);
+
+  // Offline download state
+  const [dlVisible, setDlVisible]   = useState(false);
+  const [dlName, setDlName]         = useState('');
+  const [dlProgress, setDlProgress] = useState<number | null>(null);
+  const [dlSize, setDlSize]         = useState(0);
+  const isVectorStyle = mapTileStyle === 'liberty';
 
   // Map orientation setting → MapLibre trackUserLocation value
   const trackUserLocation = mapOrientation === 'north' ? 'default'
@@ -88,6 +99,28 @@ export function RecordingScreen() {
   async function handleResume() { resume(); await startGpsRecording(); }
   async function handleStop()   { await stopGpsRecording(); stop(); nav.navigate('PostRecording'); }
 
+  async function handleDownloadConfirm() {
+    if (!dlName.trim()) { Alert.alert('Name required'); return; }
+    const bounds = await mapRef.current?.getBounds();
+    if (!bounds) { Alert.alert('Could not read map bounds'); return; }
+    const expanded = expandBounds(bounds, 5); // add 5 km buffer
+    setDlProgress(0);
+    try {
+      await downloadRegion(
+        dlName.trim(),
+        expanded,
+        (pct, _tiles, sizeBytes) => { setDlProgress(pct); setDlSize(sizeBytes); },
+        (msg) => Alert.alert('Download error', msg),
+      );
+      setDlVisible(false);
+      setDlProgress(null);
+      Alert.alert('Download complete', `"${dlName.trim()}" is now available offline.`);
+    } catch (e: any) {
+      setDlProgress(null);
+      Alert.alert('Download failed', e?.message ?? 'Unknown error');
+    }
+  }
+
   const formatDuration = (secs: number) => {
     const h = Math.floor(secs / 3600).toString().padStart(2, '0');
     const m = Math.floor((secs % 3600) / 60).toString().padStart(2, '0');
@@ -109,7 +142,7 @@ export function RecordingScreen() {
       </View>
 
       <View style={styles.mapArea}>
-        <Map mapStyle={mapStyle} style={StyleSheet.absoluteFill} logo={false} attribution={false}>
+        <Map ref={mapRef} mapStyle={mapStyle} style={StyleSheet.absoluteFill} logo={false} attribution={false}>
           <Camera
             trackUserLocation={trackUserLocation}
             initialViewState={{ zoom: 14 }}
@@ -123,10 +156,61 @@ export function RecordingScreen() {
             </GeoJSONSource>
           )}
         </Map>
-        <TouchableOpacity style={[styles.sensorBtn, { borderColor: colors.border }]} onPress={() => nav.navigate('SensorPairing')}>
+        <View style={[styles.mapOverlay, { top: insets.top > 0 ? insets.top + 8 : 10 }]}>
-          <Text style={[styles.sensorBtnText, { color: accent }]}>⚡ Sensors</Text>
+          <TouchableOpacity style={[styles.overlayBtn, { borderColor: colors.border }]} onPress={() => nav.navigate('SensorPairing')}>
+            <Text style={[styles.overlayBtnText, { color: accent }]}>⚡ Sensors</Text>
+          </TouchableOpacity>
+          {isVectorStyle && status === 'idle' && (
+            <TouchableOpacity
+              style={[styles.overlayBtn, { borderColor: colors.border }]}
+              onPress={() => { setDlName(''); setDlVisible(true); }}
+            >
+              <Text style={[styles.overlayBtnText, { color: accent }]}>↓ Offline</Text>
+            </TouchableOpacity>
+          )}
+        </View>
+      </View>
+
+      {/* Offline download modal */}
+      <Modal visible={dlVisible} transparent animationType="fade" onRequestClose={() => dlProgress === null && setDlVisible(false)}>
+        <Pressable style={styles.modalOverlay} onPress={() => dlProgress === null && setDlVisible(false)}>
+          <Pressable style={styles.modalBox} onPress={() => {}}>
+            {dlProgress === null ? (
+              <>
+                <Text style={styles.modalHeading}>Download visible area</Text>
+                <Text style={styles.modalSub}>
+                  Downloads the current map view (zoom 6–16) for offline use.{'\n'}
+                  Only available with the Liberty vector style.
+                </Text>
+                <TextInput
+                  style={styles.modalInput}
+                  value={dlName}
+                  onChangeText={setDlName}
+                  placeholder="Region name (e.g. Alps 2026)"
+                  placeholderTextColor={colors.placeholder}
+                  autoFocus
+                />
+                <View style={styles.modalButtons}>
+                  <TouchableOpacity style={styles.modalBtn} onPress={() => setDlVisible(false)}>
+                    <Text style={[styles.modalBtnText, { color: colors.textSub }]}>Cancel</Text>
+                  </TouchableOpacity>
+                  <TouchableOpacity style={[styles.modalBtn, { backgroundColor: accent }]} onPress={handleDownloadConfirm}>
+                    <Text style={[styles.modalBtnText, { color: '#fff' }]}>Download</Text>
                   </TouchableOpacity>
                 </View>
+              </>
+            ) : (
+              <>
+                <Text style={styles.modalHeading}>Downloading…</Text>
+                <View style={styles.progressBarBg}>
+                  <View style={[styles.progressBarFill, { width: `${dlProgress}%` as any, backgroundColor: accent }]} />
+                </View>
+                <Text style={styles.modalSub}>{dlProgress.toFixed(0)}% · {formatBytes(dlSize)} downloaded</Text>
+              </>
+            )}
+          </Pressable>
+        </Pressable>
+      </Modal>
 
       <View style={styles.controls}>
         <TouchableOpacity
@@ -183,8 +267,20 @@ const styles = StyleSheet.create({
   statsGrid:     { flexDirection: 'row', flexWrap: 'wrap', padding: 8, borderBottomWidth: 1, borderBottomColor: colors.border },
   statBox:       { width: '25%', padding: 8, alignItems: 'center' },
   mapArea:        { flex: 1, overflow: 'hidden' },
-  sensorBtn:     { position: 'absolute', top: 10, right: 10, backgroundColor: 'rgba(9,9,11,0.8)', borderRadius: 8, borderWidth: 1, paddingVertical: 6, paddingHorizontal: 12 },
+  mapOverlay:     { position: 'absolute', right: 10, flexDirection: 'column', gap: 8 },
-  sensorBtnText: { fontSize: 13, fontWeight: '600' },
+  overlayBtn:     { backgroundColor: 'rgba(9,9,11,0.85)', borderRadius: 8, borderWidth: 1, paddingVertical: 6, paddingHorizontal: 12 },
+  overlayBtnText: { fontSize: 13, fontWeight: '600' },
+  // Download modal
+  modalOverlay:   { flex: 1, backgroundColor: 'rgba(0,0,0,0.7)', justifyContent: 'center', padding: 32 },
+  modalBox:       { backgroundColor: colors.surface, borderRadius: 14, padding: 20, gap: 14 },
+  modalHeading:   { color: colors.text, fontSize: 17, fontWeight: '700' },
+  modalSub:       { color: colors.textMuted, fontSize: 13, lineHeight: 18 },
+  modalInput:     { backgroundColor: colors.bg, borderWidth: 1, borderColor: colors.border, color: colors.text, borderRadius: 8, padding: 12, fontSize: 15 },
+  modalButtons:   { flexDirection: 'row', gap: 10 },
+  modalBtn:       { flex: 1, borderRadius: 8, padding: 12, alignItems: 'center', backgroundColor: colors.bg, borderWidth: 1, borderColor: colors.border },
+  modalBtnText:   { fontSize: 15, fontWeight: '600' },
+  progressBarBg:  { height: 8, backgroundColor: colors.border, borderRadius: 4, overflow: 'hidden' },
+  progressBarFill:{ height: '100%', borderRadius: 4 },
   controls:      { flexDirection: 'row', alignItems: 'center', justifyContent: 'center', gap: 12, padding: 20, borderTopWidth: 1, borderTopColor: colors.border },
   awakeBtn:      { backgroundColor: colors.surface, borderRadius: 20, borderWidth: 1, borderColor: colors.border, paddingVertical: 8, paddingHorizontal: 14 },
   awakeBtnText:  { color: colors.textSub, fontSize: 13 },

src/screens/SettingsScreen.tsx

@@ -8,6 +8,7 @@ import { login, logout, loadAuthState } from '../services/auth';
 import { colors, PALETTES, type PaletteKey, type FontSizeKey } from '../theme';
 import { useTheme, type MapOrientation } from '../ThemeContext';
 import { MAP_STYLES, MAP_TILE_STYLE_ORDER } from '../mapStyles';
+import { listRegions, deleteRegion, formatBytes, type OfflineRegion } from '../services/offline';
 
 type Tab = 'ui' | 'app' | 'sync';
 
@@ -122,11 +123,13 @@ const MAP_ORIENTATION_OPTIONS: { key: MapOrientation; label: string; sub: string
 function AppTab() {
   const { accent, accentDim, mapOrientation, setMapOrientation } = useTheme();
   const [kmNotifications, setKmNotifications] = useState(true);
+  const [regions, setRegions] = useState<OfflineRegion[]>([]);
 
   useEffect(() => {
     AsyncStorage.getItem('kmNotifications').then((v) => {
       if (v !== null) setKmNotifications(v === 'true');
     });
+    listRegions().then(setRegions).catch(() => {});
   }, []);
 
   async function handleKmToggle(value: boolean) {
@@ -134,6 +137,16 @@ function AppTab() {
     await AsyncStorage.setItem('kmNotifications', String(value));
   }
 
+  async function handleDeleteRegion(id: string, name: string) {
+    Alert.alert('Delete offline region?', `"${name}" will be removed from the device.`, [
+      { text: 'Cancel', style: 'cancel' },
+      { text: 'Delete', style: 'destructive', onPress: async () => {
+        await deleteRegion(id);
+        setRegions((prev) => prev.filter((r) => r.id !== id));
+      }},
+    ]);
+  }
+
   return (
     <ScrollView contentContainerStyle={styles.content}>
       <Text style={styles.sectionTitle}>Map orientation</Text>
@@ -167,6 +180,32 @@ function AppTab() {
           thumbColor={colors.text}
         />
       </View>
+
+      <Text style={styles.sectionTitle}>Offline maps</Text>
+      {regions.length === 0 ? (
+        <View style={[styles.row, { opacity: 0.5 }]}>
+          <Text style={styles.rowSub}>
+            No offline regions yet.{'\n'}
+            Tap "↓ Offline" on the map (Liberty style) to download an area.
+          </Text>
+        </View>
+      ) : (
+        regions.map((r) => (
+          <View key={r.id} style={styles.row}>
+            <View style={{ flex: 1 }}>
+              <Text style={styles.rowLabel}>{r.name}</Text>
+              <Text style={styles.rowSub}>
+                {r.state === 'complete'
+                  ? `${formatBytes(r.totalSizeBytes)} · ${r.completedTiles} tiles`
+                  : `${r.percentage.toFixed(0)}% downloading…`}
+              </Text>
+            </View>
+            <TouchableOpacity onPress={() => handleDeleteRegion(r.id, r.name)}>
+              <Text style={{ color: colors.error, fontSize: 13, fontWeight: '600' }}>Delete</Text>
+            </TouchableOpacity>
+          </View>
+        ))
+      )}
     </ScrollView>
   );
 }

src/services/offline.ts

@@ -0,0 +1,100 @@
+import { OfflineManager, type OfflinePackStatus } from '@maplibre/maplibre-react-native';
+
+type LngLatBounds = [number, number, number, number]; // [west, south, east, north]
+
+// Vector style URL — only vector styles support offline packs
+export const OFFLINE_STYLE_URL = 'https://tiles.openfreemap.org/styles/liberty';
+
+// Zoom levels: 6 (region overview) → 16 (street detail, good for cycling)
+const MIN_ZOOM = 6;
+const MAX_ZOOM = 16;
+
+export interface OfflineRegion {
+  id: string;
+  name: string;
+  bounds: LngLatBounds;
+  createdAt: string;
+  completedTiles: number;
+  totalSizeBytes: number;
+  state: 'active' | 'inactive' | 'complete';
+  percentage: number;
+}
+
+// ── Download ──────────────────────────────────────────────────────────────────
+
+export async function downloadRegion(
+  name: string,
+  bounds: LngLatBounds,
+  onProgress: (pct: number, tilesDown: number, sizeBytes: number) => void,
+  onError: (msg: string) => void,
+): Promise<string> {
+  OfflineManager.setProgressEventThrottle(500);
+
+  const pack = await OfflineManager.createPack(
+    {
+      mapStyle: OFFLINE_STYLE_URL,
+      bounds,
+      minZoom: MIN_ZOOM,
+      maxZoom: MAX_ZOOM,
+      metadata: { name, createdAt: new Date().toISOString() },
+    },
+    (_pack, status: OfflinePackStatus) => {
+      onProgress(status.percentage, status.completedTileCount, status.completedTileSize);
+    },
+    (_pack, error) => {
+      onError(error.message);
+    },
+  );
+
+  return pack.id;
+}
+
+// ── List ──────────────────────────────────────────────────────────────────────
+
+export async function listRegions(): Promise<OfflineRegion[]> {
+  const packs = await OfflineManager.getPacks();
+  const regions: OfflineRegion[] = [];
+
+  for (const pack of packs) {
+    const status = await pack.status();
+    const meta = pack.metadata as { name?: string; createdAt?: string };
+    regions.push({
+      id: pack.id,
+      name: meta.name ?? 'Unnamed region',
+      bounds: pack.bounds,
+      createdAt: meta.createdAt ?? '',
+      completedTiles: status.completedTileCount,
+      totalSizeBytes: status.completedTileSize,
+      state: status.state,
+      percentage: status.percentage,
+    });
+  }
+
+  return regions;
+}
+
+// ── Delete ────────────────────────────────────────────────────────────────────
+
+export async function deleteRegion(id: string): Promise<void> {
+  await OfflineManager.deletePack(id);
+}
+
+// ── Helpers ───────────────────────────────────────────────────────────────────
+
+export function formatBytes(bytes: number): string {
+  if (bytes < 1024) return `${bytes} B`;
+  if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)} KB`;
+  return `${(bytes / (1024 * 1024)).toFixed(1)} MB`;
+}
+
+/** Expand a [w,s,e,n] bounds by `km` kilometres in every direction. */
+export function expandBounds(bounds: LngLatBounds, km: number): LngLatBounds {
+  const latDelta = km / 111;
+  const lonDelta = km / (111 * Math.cos((bounds[1] + bounds[3]) / 2 * Math.PI / 180));
+  return [
+    bounds[0] - lonDelta,
+    bounds[1] - latDelta,
+    bounds[2] + lonDelta,
+    bounds[3] + latDelta,
+  ];
+}