feat: add reset synced data button to settings

mobile/app/(tabs)/settings.tsx

@@ -4,7 +4,7 @@ import {
   ActivityIndicator, Platform, Pressable, ScrollView, StyleSheet,
   Text, TextInput, View,
 } from 'react-native';
-import { getSetting, setSetting, useSetting } from '@/db/queries';
+import { deleteRemoteActivities, getSetting, setSetting, useSetting } from '@/db/queries';
 
 export default function SettingsScreen() {
   const db = useSQLiteContext();
@@ -23,6 +23,9 @@ export default function SettingsScreen() {
   const [connecting,  setConnecting]  = useState(false);
   const [connectMsg,  setConnectMsg]  = useState<{ ok: boolean; text: string } | null>(null);
 
+  const [resetArmed,  setResetArmed]  = useState(false);
+  const [resetMsg,    setResetMsg]    = useState<string | null>(null);
+
   async function save() {
     await setSetting(db, 'instance_url', instanceUrl.trim());
     await setSetting(db, 'handle', handle.trim());
@@ -71,6 +74,17 @@ export default function SettingsScreen() {
     setConnectMsg(null);
   }
 
+  async function resetSyncedData() {
+    if (!resetArmed) {
+      setResetArmed(true);
+      return;
+    }
+    const n = await deleteRemoteActivities(db);
+    setResetArmed(false);
+    setResetMsg(`Removed ${n} synced ${n === 1 ? 'activity' : 'activities'}`);
+    setTimeout(() => setResetMsg(null), 3000);
+  }
+
   const isConnected = !!storedToken;
 
   return (
@@ -160,6 +174,22 @@ export default function SettingsScreen() {
         </Section>
       )}
 
+      <Section title="Data">
+        <Pressable
+          style={[styles.resetButton, resetArmed && styles.resetButtonArmed]}
+          onPress={resetSyncedData}
+          onBlur={() => setResetArmed(false)}
+        >
+          <Text style={[styles.resetText, resetArmed && styles.resetTextArmed]}>
+            {resetArmed ? 'Tap again to confirm' : 'Reset synced data'}
+          </Text>
+        </Pressable>
+        {resetMsg && <Text style={styles.msgOk}>{resetMsg}</Text>}
+        <Text style={styles.hint}>
+          Removes all activities synced from the instance. Locally imported files are kept.
+        </Text>
+      </Section>
+
       <Section title="About">
         <Row label="Version" value="0.1.0 (Phase 0.5)" />
         <Row label="Schema"  value="BAS 1.0" />
@@ -252,4 +282,11 @@ const styles = StyleSheet.create({
   disconnectText: { color: '#71717a', fontSize: 14 },
   msgOk:  { color: '#86efac', fontSize: 13, paddingHorizontal: 12, paddingBottom: 10 },
   msgErr: { color: '#fca5a5', fontSize: 13, paddingHorizontal: 12, paddingBottom: 10 },
+  resetButton: {
+    margin: 12, paddingVertical: 10, alignItems: 'center',
+    borderRadius: 8, borderWidth: 1, borderColor: '#3f3f46',
+  },
+  resetButtonArmed: { borderColor: '#ef4444', backgroundColor: '#1c0a0a' },
+  resetText:        { color: '#71717a', fontSize: 14 },
+  resetTextArmed:   { color: '#ef4444', fontWeight: '600' },
 });

mobile/db/queries.ts

@@ -103,6 +103,13 @@ export async function upsertRemoteActivity(
   return result.changes > 0;
 }
 
+export async function deleteRemoteActivities(
+  db: ReturnType<typeof useSQLiteContext>,
+): Promise<number> {
+  const result = await db.runAsync(`DELETE FROM activities WHERE origin = 'remote'`);
+  return result.changes;
+}
+
 // ── Settings ───────────────────────────────────────────────────────────────
 
 export async function getSetting(