Add LLM digest setup and share timestamp context

lib/features/ai_digest/data/llm_digest_config.dart

@@ -7,6 +7,7 @@ const String _preferredWeekdayKey = 'llm_digest_preferred_weekday';
 const String _preferredHourKey = 'llm_digest_preferred_hour';
 const String _requireWifiKey = 'llm_digest_require_wifi';
 const String _requireChargingKey = 'llm_digest_require_charging';
+const String _enableWebSearchKey = 'llm_digest_enable_web_search';
 
 class LlmDigestConfigNotifier extends Notifier<LlmDigestConfigState> {
   Future<void>? _initializeFuture;
@@ -29,6 +30,7 @@ class LlmDigestConfigNotifier extends Notifier<LlmDigestConfigState> {
       preferredHour: prefs.getInt(_preferredHourKey) ?? 21,
       requireWifi: prefs.getBool(_requireWifiKey) ?? true,
       requireCharging: prefs.getBool(_requireChargingKey) ?? true,
+      enableWebSearch: prefs.getBool(_enableWebSearchKey) ?? true,
     );
   }
 
@@ -68,6 +70,12 @@ class LlmDigestConfigNotifier extends Notifier<LlmDigestConfigState> {
       requireCharging: requireCharging,
     );
   }
+
+  Future<void> setWebSearchEnabled(bool enabled) async {
+    final SharedPreferences prefs = await SharedPreferences.getInstance();
+    await prefs.setBool(_enableWebSearchKey, enabled);
+    state = state.copyWith(enableWebSearch: enabled);
+  }
 }
 
 final NotifierProvider<LlmDigestConfigNotifier, LlmDigestConfigState>