MobileFix - Resilience: Background retry policy for failed mutations (Part 4 of 6)

[palisadoes]

Problem Statement

No retry/backoff for failed mutations; add queue.

Files to Modify / Create (static targets)

• lib/services/retry_queue.dart
• lib/services/**
• test/unit/services/retry_queue_test.dart

Files to Modify / Create (detected for this PR)

• lib/view_model/after_auth_view_models/event_view_models/edit_event_view_model.dart
• lib/view_model/after_auth_view_models/event_view_models/event_info_view_model.dart
• lib/view_model/after_auth_view_models/event_view_models/manage_volunteer_group_view_model.dart
• lib/view_model/after_auth_view_models/feed_view_models/organization_feed_view_model.dart
• lib/view_model/after_auth_view_models/fund_view_model/fund_view_model.dart
• lib/view_model/connectivity_view_model.dart
• lib/view_model/pre_auth_view_models/login_view_model.dart
• lib/view_model/pre_auth_view_models/select_organization_view_model.dart
• lib/view_model/pre_auth_view_models/set_url_view_model.dart
• lib/view_model/pre_auth_view_models/signup_details_view_model.dart

Proposed Solution

Implement within MVVM + Provider + GetIt; avoid large rewrites. Keep changes scoped to the listed files.

Implementation Approach

1. Update only the files listed above (<= 10 in this PR).
2. Add/adjust tests accordingly; keep CI green.
3. If more files are needed, open follow-up PRs.

Acceptance Criteria

• All listed files updated
• Tests added/updated (>= 80% for changed units)
• CI passing
• Docs updated if applicable

Starter Code

Starter Code

// lib/services/retry_queue.dart
import 'dart:async';
typedef Task<T>=Future<T> Function();
class RetryQueue{
  static final Map<String,Task<dynamic>> _q={};
  static Future<T> enqueue<T>(Task<T> task,{required String key,Duration initial=const Duration(milliseconds:300)}) async{
    _q[key]=task; var delay=initial;
    for(var i=0;i<3;i++){ try{ final r=await task(); _q.remove(key); return r; }catch(_){ await Future.delayed(delay); delay*=2; } }
    rethrow;
  }
}

Dependencies

• Blocked by: MobileFix - Resilience: Background retry policy for failed mutations (Part 3 of 6) #3205, MobileFix - Architecture: Standardize a Result/Error model across services (Part 6 of 6) #3183
• Blocks: MobileFix - Resilience: Background retry policy for failed mutations (Part 5 of 6) #3207

Phase

P2 - High Impact

[github-actions]

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