feat: implement settings screen with reminders, biometrics, theme, and PDF export

- Daily reminder scheduling via flutter_local_notifications (inexact, repeating at chosen time)
- Biometric lock gate on app launch with auto-prompt and manual unlock button
- Theme mode selector (System/Light/Dark) persisted to settings DB
- PDF export of full mood history shared via share_plus
- Android: POST_NOTIFICATIONS, USE_BIOMETRIC permissions; switched to FlutterFragmentActivity

lib/core/database/daos/mood_dao.dart

@@ -55,6 +55,11 @@ class MoodDao extends DatabaseAccessor<AppDatabase> with _$MoodDaoMixin {
 
   // ── Reads ───────────────────────────────────────────────────────────────────
 
+  Future<List<MoodEntry>> getAllEntries() =>
+      (select(moodEntries)
+            ..orderBy([(t) => OrderingTerm.asc(t.timestamp)]))
+          .get();
+
   Stream<List<MoodEntry>> watchAllEntries() =>
       (select(moodEntries)..orderBy([(t) => OrderingTerm.desc(t.timestamp)]))
           .watch();