Add Phase 2 community features: clubs and challenges (FRE-4664)

Implement full MVVM stack for two new community features:

Clubs:
- Persistent runner groups with type, privacy, and member management
- Club discovery, creation, join/leave, and invite workflows
- Member roles (Owner, Admin, Member) and capacity limits

Challenges:
- Time-bound competitive goals with progress tracking and leaderboards
- Challenge types: distance, time, frequency, elevation, calories, streak
- Progress submission, participation status, and ranking

Files:
- Models: Club.swift, Challenge.swift
- Services: ClubService.swift, ChallengeService.swift
- ViewModels: ClubViewModel.swift, ChallengeViewModel.swift
- Views: ClubsView.swift, ClubDetailView.swift, ChallengesView.swift, ChallengeDetailView.swift
- Tests: ClubServiceTests.swift, ChallengeServiceTests.swift
- Updated README.md with new feature documentation

Lendair/README.md

@@ -20,21 +20,27 @@ Lendair/
 │   ├── Race.swift                  # Race, RaceType, RaceFilter, API response types
 │   ├── FamilyPlan.swift            # FamilyPlan, FamilyMember, LeaderboardMetric
 │   ├── BeginnerMode.swift          # BeginnerConfig, Milestone, OnboardingStep
-│   └── CommunityEvent.swift        # CommunityEvent, EventType, RSVPStatus
+│   ├── CommunityEvent.swift        # CommunityEvent, EventType, RSVPStatus
+│   ├── Club.swift                  # Club, ClubType, ClubPrivacy, MembershipStatus, ClubMember
+│   └── Challenge.swift             # Challenge, ChallengeType, ChallengeStatus, LeaderboardEntry
 ├── Services/
 │   ├── NotificationService.swift   # NotificationsServiceProtocol + implementation
 │   ├── TrainingPlanService.swift   # TrainingPlanServiceProtocol + implementation
 │   ├── RaceService.swift           # RaceServiceProtocol + implementation
 │   ├── FamilyPlanService.swift     # FamilyPlanServiceProtocol + implementation
 │   ├── BeginnerModeService.swift   # BeginnerModeServiceProtocol + implementation
-│   └── CommunityEventService.swift # CommunityEventServiceProtocol + implementation
+│   ├── CommunityEventService.swift # CommunityEventServiceProtocol + implementation
+│   ├── ClubService.swift           # ClubServiceProtocol + implementation
+│   └── ChallengeService.swift      # ChallengeServiceProtocol + implementation
 ├── ViewModels/
 │   ├── NotificationsViewModel.swift
 │   ├── TrainingPlanViewModel.swift
 │   ├── RaceDiscoveryViewModel.swift
 │   ├── FamilyPlanViewModel.swift
 │   ├── BeginnerModeViewModel.swift
-│   └── CommunityEventViewModel.swift
+│   ├── CommunityEventViewModel.swift
+│   ├── ClubViewModel.swift
+│   └── ChallengeViewModel.swift
 ├── Views/
 │   ├── NotificationsView.swift
 │   ├── NotificationRowView.swift
@@ -47,7 +53,11 @@ Lendair/
 │   ├── FamilyMemberView.swift
 │   ├── BeginnerModeView.swift
 │   ├── CommunityEventsView.swift
-│   └── CommunityEventDetailView.swift
+│   ├── CommunityEventDetailView.swift
+│   ├── ClubsView.swift
+│   ├── ClubDetailView.swift
+│   ├── ChallengesView.swift
+│   └── ChallengeDetailView.swift
 └── README.md
 ```
 
@@ -95,6 +105,24 @@ Lendair/
 - Participant tracking
 - Upcoming/ongoing/past event categorization
 
+### Clubs (Phase 2 - Community)
+- Persistent community groups for runners and fitness enthusiasts
+- Club types: Running, Walking, Cycling, Triathlon, CrossFit, General Fitness
+- Privacy levels: Public, Private, Invitation Only
+- Member management with roles (Owner, Admin, Member)
+- Invite members via email
+- Club rules and capacity limits
+- Discover clubs by type, location, and privacy
+
+### Challenges (Phase 2 - Community)
+- Time-bound competitive goals with progress tracking
+- Challenge types: Distance, Time, Frequency, Elevation, Calories, Streak
+- Real-time leaderboard with rankings
+- Progress submission and percentage tracking
+- Join/leave challenges
+- Create custom challenges with rules and targets
+- Active/upcoming/completed challenge categorization
+
 ## Service Pattern
 
 All services follow the same architecture:
@@ -154,23 +182,48 @@ All services follow the same architecture:
 | PATCH | `/api/events/:id` | Update event |
 | POST | `/api/events/:id/rsvp` | RSVP to event |
 
+### Clubs
+| Method | Endpoint | Description |
+|--------|----------|-------------|
+| GET | `/api/clubs?type=&privacy=&...` | List clubs with filters |
+| GET | `/api/clubs/:id` | Get club detail with members |
+| POST | `/api/clubs` | Create club |
+| PATCH | `/api/clubs/:id` | Update club |
+| POST | `/api/clubs/:id/join` | Join club |
+| POST | `/api/clubs/:id/leave` | Leave club |
+| POST | `/api/clubs/:id/invite` | Invite member by email |
+| DELETE | `/api/clubs/:id/members/:memberId` | Remove member |
+
+### Challenges
+| Method | Endpoint | Description |
+|--------|----------|-------------|
+| GET | `/api/challenges?type=&status=&...` | List challenges with filters |
+| GET | `/api/challenges/:id` | Get challenge detail with participants |
+| POST | `/api/challenges` | Create challenge |
+| PATCH | `/api/challenges/:id` | Update challenge |
+| POST | `/api/challenges/:id/join` | Join challenge |
+| POST | `/api/challenges/:id/leave` | Leave challenge |
+| GET | `/api/challenges/:id/leaderboard` | Get challenge leaderboard |
+| POST | `/api/challenges/:id/progress` | Submit progress |
+
 ## Testing
 
 Tests are in `LendairTests/`:
 - Uses mock services conforming to feature protocols
 - ViewModel tests cover fetch, update, error handling, and computed properties
-- Model tests cover enum cases, display values, and equality
+- Model tests cover enum cases, display values, equality, and computed properties
+- Available test files: `NotificationServiceTests.swift`, `ClubServiceTests.swift`, `ChallengeServiceTests.swift`
 
 ## Usage
 
 ```swift
 // Feature views can be integrated into your navigation stack
 NavigationStack {
-    TrainingPlanView()
+    ClubsView()
 }
 
 NavigationStack {
-    RaceDiscoveryView()
+    ChallengesView()
 }
 
 NavigationStack {