feat(ios): add error handling and integration tests

Implement comprehensive error handling and integration test suite:

Error Handling (Section 8):
- Add iOS-specific error codes to DailyNotificationErrorCodes:
  - NOTIFICATION_PERMISSION_DENIED
  - PENDING_NOTIFICATION_LIMIT_EXCEEDED
  - BG_TASK_NOT_REGISTERED
  - BG_TASK_EXECUTION_FAILED
  - BACKGROUND_REFRESH_DISABLED
- Add helper methods for iOS-specific error responses
- Enhance error handling in ReactivationManager:
  - Database errors handled gracefully (non-fatal)
  - Notification center errors handled gracefully (non-fatal)
  - Scheduling errors handled gracefully (non-fatal)
  - All errors logged, app continues normally
  - Partial results returned when operations fail
- Update plugin methods to use iOS-specific error codes:
  - getNotificationPermissionStatus uses NOTIFICATION_PERMISSION_DENIED

Integration Tests (Section 9.2):
- Add DailyNotificationRecoveryIntegrationTests:
  - Full recovery flow tests (cold start, termination)
  - Error handling tests (database, notification center, scheduling)
  - App stability tests (no crashes, concurrent operations)
  - Partial recovery tests
  - Timeout handling tests
- Test coverage:
  - 10 integration tests covering recovery scenarios
  - Error handling verification
  - App stability verification
  - Concurrent operation safety

Completes sections 8.1, 8.2, and 9.2 of iOS implementation checklist.

docs/IOS_IMPLEMENTATION_CHECKLIST.md

@@ -381,22 +381,22 @@ Complete checklist of iOS code that needs to be implemented for feature parity w
 
 ### 8.1 Recovery Error Handling
 
-- [ ] Ensure all recovery methods catch errors:
-  - [ ] Database errors (non-fatal)
-  - [ ] Notification center errors (non-fatal)
-  - [ ] Scheduling errors (non-fatal)
-- [ ] Log errors but don't crash app
-- [ ] Return partial results if some operations fail
+- [x] Ensure all recovery methods catch errors:
+  - [x] Database errors (non-fatal) - handled in detectScenario, detectMissedNotifications, verifyFutureNotifications
+  - [x] Notification center errors (non-fatal) - handled in detectScenario, verifyFutureNotifications
+  - [x] Scheduling errors (non-fatal) - handled in rescheduleMissingNotification
+- [x] Log errors but don't crash app - all errors logged with NSLog, app continues
+- [x] Return partial results if some operations fail - RecoveryResult includes error count
 
 ### 8.2 Error Types
 
-- [ ] Define iOS-specific error codes:
-  - [ ] `NOTIFICATION_PERMISSION_DENIED`
-  - [ ] `BACKGROUND_REFRESH_DISABLED`
-  - [ ] `PENDING_NOTIFICATION_LIMIT_EXCEEDED`
-  - [ ] `BG_TASK_NOT_REGISTERED`
-  - [ ] `BG_TASK_EXECUTION_FAILED`
-- [ ] Map to error responses in plugin methods
+- [x] Define iOS-specific error codes:
+  - [x] `NOTIFICATION_PERMISSION_DENIED`
+  - [x] `BACKGROUND_REFRESH_DISABLED`
+  - [x] `PENDING_NOTIFICATION_LIMIT_EXCEEDED`
+  - [x] `BG_TASK_NOT_REGISTERED`
+  - [x] `BG_TASK_EXECUTION_FAILED`
+- [x] Map to error responses in plugin methods - getNotificationPermissionStatus uses NOTIFICATION_PERMISSION_DENIED
 
 ---
 
@@ -420,16 +420,16 @@ Complete checklist of iOS code that needs to be implemented for feature parity w
 
 ### 9.2 Integration Tests
 
-- [ ] Test full recovery flow:
-  - [ ] Schedule notification
-  - [ ] Terminate app
-  - [ ] Launch app
-  - [ ] Verify recovery executed
-  - [ ] Verify notifications rescheduled
-- [ ] Test error handling:
-  - [ ] Test database errors
-  - [ ] Test notification center errors
-  - [ ] Verify app doesn't crash
+- [x] Test full recovery flow:
+  - [x] Schedule notification
+  - [x] Terminate app (simulated by clearing notifications)
+  - [x] Launch app (simulated by calling performRecovery)
+  - [x] Verify recovery executed
+  - [x] Verify notifications rescheduled (DailyNotificationRecoveryIntegrationTests)
+- [x] Test error handling:
+  - [x] Test database errors (testErrorHandling_DatabaseError)
+  - [x] Test notification center errors (testErrorHandling_NotificationCenterError)
+  - [x] Verify app doesn't crash (all stability tests)
 
 ### 9.3 Manual Testing