refactor(receiver): remove setFetchTime() call from DailyNotificationReceiver

- Remove setFetchTime() call as fetchedAt is now set in constructor
- Align with new immutable timestamp model
- Ensure consistent timestamp handling across all components

This completes the migration to the new timestamp model where
fetchedAt is immutable and set at object creation time.

android/plugin/src/main/java/com/timesafari/dailynotification/DailyNotificationReceiver.java

@@ -203,7 +203,7 @@ public class DailyNotificationReceiver extends BroadcastReceiver {
             nextContent.setSound(content.isSound());
             nextContent.setPriority(content.getPriority());
             nextContent.setUrl(content.getUrl());
-            nextContent.setFetchTime(System.currentTimeMillis());
+            // fetchedAt is set in constructor, no need to set it again
             
             // Save to storage
             DailyNotificationStorage storage = new DailyNotificationStorage(context);