feat(mobile): editable activity title for local activities

Adds edits_json column (migration v3) to store user overrides separately
from detail_json so Option A server re-extraction never clobbers them.

- Tap the title in the detail screen to edit (local activities only, shown
  with a ✎ hint). Saves on keyboard dismiss via onEndEditing.
- Cards and search display user_title ?? title.
- Raw upload: user_title sent to server -> sidecar written so web UI shows
  the correct title (server re-extracts from FIT, which has Karoo's title).
- BAS upload: detail.title overridden before sending, no sidecar needed.

mobile/app/activity/[id].tsx

@@ -2,10 +2,10 @@ import { Camera, GeoJSONSource, Layer, Map } from '@maplibre/maplibre-react-nati
 import * as FileSystem from 'expo-file-system';
 import { useLocalSearchParams, useRouter } from 'expo-router';
 import { useEffect, useRef, useState } from 'react';
-import { Alert, Modal, Platform, Pressable, ScrollView, StyleSheet, Text, View } from 'react-native';
+import { Alert, Modal, Platform, Pressable, ScrollView, StyleSheet, Text, TextInput, View } from 'react-native';
 import Svg, { Defs, LinearGradient, Path, Stop } from 'react-native-svg';
 import { useSQLiteContext } from 'expo-sqlite';
-import { deleteActivity, useActivity, useSetting } from '@/db/queries';
+import { deleteActivity, setActivityTitle, useActivity, useSetting } from '@/db/queries';
 import { useTheme } from '@/ThemeContext';
 
 const MAP_STYLE = 'https://basemaps.cartocdn.com/gl/dark-matter-gl-style/style.json';
@@ -38,6 +38,8 @@ export default function ActivityScreen() {
   const [timeseries, setTimeseries] = useState<Timeseries | null>(null);
   const [loadingMap, setLoadingMap] = useState(false);
   const [loadingChart, setLoadingChart] = useState(false);
+  const [editingTitle, setEditingTitle] = useState(false);
+  const [titleDraft, setTitleDraft] = useState('');
 
   async function confirmDelete() {
     Alert.alert(
@@ -103,6 +105,9 @@ export default function ActivityScreen() {
   }
 
   const detail = JSON.parse(row.detail_json);
+  const edits = row.edits_json ? JSON.parse(row.edits_json) : {};
+  const displayTitle = edits.title ?? detail.title;
+  const canEdit = row.origin === 'local';
   const km          = detail.distance_m != null ? (detail.distance_m / 1000).toFixed(2) : null;
   const elev        = detail.elevation_gain_m != null ? Math.round(detail.elevation_gain_m) : null;
   const elevLoss    = detail.elevation_loss_m != null ? Math.round(Math.abs(detail.elevation_loss_m)) : null;
@@ -126,7 +131,30 @@ export default function ActivityScreen() {
       </View>
 
       <Text style={styles.sport}>{detail.sport ?? 'Activity'}</Text>
-      <Text style={styles.title}>{detail.title}</Text>
+      {editingTitle ? (
+        <TextInput
+          style={styles.titleInput}
+          value={titleDraft}
+          onChangeText={setTitleDraft}
+          autoFocus
+          returnKeyType="done"
+          onEndEditing={(e) => {
+            const trimmed = e.nativeEvent.text.trim();
+            if (trimmed && trimmed !== displayTitle) {
+              setActivityTitle(db, id, trimmed);
+            }
+            setEditingTitle(false);
+          }}
+        />
+      ) : (
+        <Pressable
+          onPress={canEdit ? () => { setTitleDraft(displayTitle); setEditingTitle(true); } : undefined}
+          style={styles.titleRow}
+        >
+          <Text style={styles.title}>{displayTitle}</Text>
+          {canEdit && <Text style={styles.editHint}>✎</Text>}
+        </Pressable>
+      )}
       <Text style={styles.date}>{date}</Text>
 
       {/* Map */}
@@ -468,7 +496,10 @@ const styles = StyleSheet.create({
   deleteButton:   { paddingHorizontal: 16 },
   deleteText:     { color: '#f87171', fontSize: 15 },
   sport:          { color: '#71717a', fontSize: 12, fontWeight: '600', letterSpacing: 0.8, paddingHorizontal: 16, marginBottom: 4 },
-  title:          { color: '#f4f4f5', fontSize: 22, fontWeight: '700', paddingHorizontal: 16, marginBottom: 4 },
+  titleRow:       { flexDirection: 'row', alignItems: 'center', paddingHorizontal: 16, marginBottom: 4 },
+  title:          { color: '#f4f4f5', fontSize: 22, fontWeight: '700', flexShrink: 1 },
+  titleInput:     { color: '#f4f4f5', fontSize: 22, fontWeight: '700', paddingHorizontal: 16, marginBottom: 4, borderBottomWidth: 1, borderBottomColor: '#3b82f6' },
+  editHint:       { color: '#52525b', fontSize: 16, marginLeft: 8 },
   date:           { color: '#71717a', fontSize: 13, paddingHorizontal: 16, marginBottom: 16 },
   mapContainer:    { height: 220, marginBottom: 16, borderTopWidth: 1, borderBottomWidth: 1, borderColor: '#27272a' },
   map:             { flex: 1 },