feat: tap map thumbnail to open full-screen interactive map

mobile/app/activity/[id].tsx

@@ -1,7 +1,7 @@
 import { Camera, GeoJSONSource, Layer, Map } from '@maplibre/maplibre-react-native';
 import { useLocalSearchParams, useRouter } from 'expo-router';
 import { useEffect, useState } from 'react';
-import { ActivityIndicator, Pressable, ScrollView, StyleSheet, Text, View } from 'react-native';
+import { ActivityIndicator, Modal, Pressable, ScrollView, StyleSheet, Text, View } from 'react-native';
 import Svg, { Defs, LinearGradient, Path, Stop } from 'react-native-svg';
 import { useActivity, useSetting } from '@/db/queries';
 
@@ -121,6 +121,8 @@ export default function ActivityScreen() {
 // ── Map ───────────────────────────────────────────────────────────────────────
 
 function RouteMap({ geojson, loading }: { geojson: object | null; loading: boolean }) {
+  const [fullscreen, setFullscreen] = useState(false);
+
   if (loading) {
     return (
       <View style={styles.mapPlaceholder}>
@@ -131,25 +133,7 @@ function RouteMap({ geojson, loading }: { geojson: object | null; loading: boole
   if (!geojson) return null;
 
   const bounds = geoJsonBounds(geojson);
-
-  return (
-    <View style={styles.mapContainer}>
-      <Map
-        style={styles.map}
-        mapStyle={MAP_STYLE}
-        dragPan={false}
-        touchZoom={false}
-        touchPitch={false}
-        touchRotate={false}
-      >
-        {bounds && (
-          <Camera
-            initialViewState={{
-              bounds,
-              padding: { top: 24, bottom: 24, left: 24, right: 24 },
-            }}
-          />
-        )}
+  const routeSource = (
     <GeoJSONSource id="route" data={geojson as GeoJSON.FeatureCollection}>
       <Layer
         type="line"
@@ -158,8 +142,49 @@ function RouteMap({ geojson, loading }: { geojson: object | null; loading: boole
         layout={{ 'line-cap': 'round', 'line-join': 'round' }}
       />
     </GeoJSONSource>
+  );
+  const camera = bounds ? (
+    <Camera
+      initialViewState={{
+        bounds,
+        padding: { top: 24, bottom: 24, left: 24, right: 24 },
+      }}
+    />
+  ) : null;
+
+  return (
+    <>
+      {/* Thumbnail — tap to expand */}
+      <Pressable style={styles.mapContainer} onPress={() => setFullscreen(true)}>
+        <Map
+          style={styles.map}
+          mapStyle={MAP_STYLE}
+          dragPan={false}
+          touchZoom={false}
+          touchPitch={false}
+          touchRotate={false}
+        >
+          {camera}
+          {routeSource}
         </Map>
+        <View style={styles.mapExpandHint}>
+          <Text style={styles.mapExpandText}>⤢ tap to explore</Text>
         </View>
+      </Pressable>
+
+      {/* Full-screen interactive map */}
+      <Modal visible={fullscreen} animationType="slide" onRequestClose={() => setFullscreen(false)}>
+        <View style={styles.fullscreenMap}>
+          <Map style={styles.map} mapStyle={MAP_STYLE}>
+            {camera}
+            {routeSource}
+          </Map>
+          <Pressable style={styles.closeButton} onPress={() => setFullscreen(false)}>
+            <Text style={styles.closeText}>✕</Text>
+          </Pressable>
+        </View>
+      </Modal>
+    </>
   );
 }
 
@@ -281,6 +306,11 @@ const styles = StyleSheet.create({
   mapContainer:    { height: 220, marginBottom: 16, borderTopWidth: 1, borderBottomWidth: 1, borderColor: '#27272a' },
   map:             { flex: 1 },
   mapPlaceholder:  { height: 220, backgroundColor: '#18181b', alignItems: 'center', justifyContent: 'center', borderTopWidth: 1, borderBottomWidth: 1, borderColor: '#27272a', marginBottom: 16 },
+  mapExpandHint:   { position: 'absolute', bottom: 8, right: 8, backgroundColor: 'rgba(0,0,0,0.55)', borderRadius: 6, paddingHorizontal: 8, paddingVertical: 4 },
+  mapExpandText:   { color: '#a1a1aa', fontSize: 11 },
+  fullscreenMap:   { flex: 1, backgroundColor: '#09090b' },
+  closeButton:     { position: 'absolute', top: 56, right: 16, backgroundColor: 'rgba(0,0,0,0.6)', borderRadius: 20, width: 36, height: 36, alignItems: 'center', justifyContent: 'center' },
+  closeText:       { color: '#fff', fontSize: 16 },
   chartContainer: { marginHorizontal: 16, marginBottom: 16, backgroundColor: '#18181b', borderRadius: 10, borderWidth: 1, borderColor: '#27272a', padding: 12, alignItems: 'flex-start' },
   chartPlaceholder: { height: 120, backgroundColor: '#18181b', alignItems: 'center', justifyContent: 'center', borderRadius: 10, borderWidth: 1, borderColor: '#27272a', marginHorizontal: 16, marginBottom: 16 },
   chartLabel:     { color: '#3f3f46', fontSize: 10, marginBottom: 2 },