feat(android): add fetch scheduling debug logs and triggerImmediateFetch API

- Add DN|SCHEDULE_CALLBACK logs to diagnose fetch scheduling
- Add DN|SCHEDULE_FETCH_* structured logs for traceability
- Add triggerImmediateFetch() public API for standalone fetches
- Update fetch timing from 1 hour to 5 minutes before notification
- Fix TypeScript lint errors: add return types, replace any types
- Fix ESLint warnings: add console suppression comments
- Fix capacitor.settings.gradle plugin path reference
- Update android-app-improvement-plan.md with current state

Changes:
- DailyNotificationPlugin: Added scheduled callback logging and fetch method
- DailyNotificationFetcher: Changed lead time from 1 hour to 5 minutes
- EnhancedDailyNotificationFetcher: Added ENH|* structured event IDs
- TypeScript services: Fixed lint errors and added proper types
- Test app: Fixed capacitor settings path and TypeScript warnings

src/definitions.ts

@@ -374,6 +374,21 @@ export interface DailyNotificationPlugin {
   clearCacheForNewIdentity(): Promise<void>;
   updateBackgroundTaskIdentity(activeDid: string): Promise<void>;
 
+  // Content Fetching Methods
+  /**
+   * Trigger an immediate standalone fetch for content updates
+   * 
+   * This method allows manual triggering of content fetches independently of 
+   * scheduled notifications. Useful for on-demand content refresh, cache warming,
+   * or background sync operations.
+   * 
+   * @returns Promise with success status and message
+   */
+  triggerImmediateFetch(): Promise<{
+    success: boolean;
+    message: string;
+  }>;
+
   // Static Daily Reminder Methods
   /**
    * Schedule a simple daily reminder notification