Add failure backoff for sync auto triggers

docs/progress.md

@@ -2,6 +2,23 @@
 
 Updated: 2026-02-15
 
+## Latest Milestone (2026-02-15): Sync Auto-Trigger Backoff
+
+Improved sync trigger resilience for repeated failures:
+
+- Updated `lib/features/sync/sync_auto_trigger_controller.dart`:
+  - tracks consecutive sync failures
+  - applies exponential cooldown backoff before auto-trigger retries
+  - resets backoff after a successful sync run
+- Added coverage:
+  - `test/features/sync/sync_auto_trigger_controller_test.dart`
+  - validates cooldown behavior after failures
+
+Validation for this milestone:
+
+- `flutter analyze` -> pass
+- `flutter test` -> pass
+
 ## Latest Milestone (2026-02-15): Reminder Delivery Interface Wiring
 
 Implemented the notification scheduling boundary and connected it to local data
@@ -68,7 +85,7 @@ Validation for this milestone:
    - current UX shows and dismisses rejections; still missing guided
      resolve/retry/inspect flows per entity.
 3. Sync trigger maturity:
-   - add connectivity-aware triggers and backoff policy for repeated failures.
+   - connectivity-aware triggers are still missing.
 4. Test depth:
    - add integration tests for auth + sync + CRUD end-to-end app flows.