FRE-4665: Implement Phase 3 AI training plans and premium features

- Models: TrainingPlan, Race, FamilyPlan, BeginnerMode, CommunityEvent
- Services: 5 service layers with protocol-based architecture
- ViewModels: 5 view models with @MainActor ObservableObject pattern
- Views: 10 SwiftUI views for all Phase 3 features
- Updated README with full Phase 3 documentation

Co-Authored-By: Paperclip <noreply@paperclip.ing>

Lendair/ViewModels/RaceDiscoveryViewModel.swift

@@ -0,0 +1,106 @@
+import Foundation
+import SwiftUI
+
+@MainActor
+class RaceDiscoveryViewModel: ObservableObject {
+    @Published var races: [Race] = []
+    @Published var savedRaces: [Race] = []
+    @Published var selectedRace: Race?
+    @Published var isLoading: Bool = false
+    @Published var error: RaceError?
+    @Published var filter: RaceFilter = RaceFilter()
+
+    private let service: RaceServiceProtocol
+
+    init(service: RaceServiceProtocol = RaceService()) {
+        self.service = service
+    }
+
+    func fetchRaces() async {
+        isLoading = true
+        error = nil
+        defer { isLoading = false }
+
+        do {
+            races = try await service.listRaces(filter: filter)
+        } catch let error as RaceError {
+            self.error = error
+        } catch {
+            print("Failed to fetch races: \(error)")
+        }
+    }
+
+    func selectRace(id: String) async {
+        isLoading = true
+        error = nil
+        defer { isLoading = false }
+
+        do {
+            let race = try await service.getRace(id: id)
+            selectedRace = race
+            if let index = races.firstIndex(where: { $0.id == id }) {
+                races[index] = race
+                objectWillChange.send()
+            }
+        } catch let error as RaceError {
+            self.error = error
+        } catch {
+            print("Failed to get race: \(error)")
+        }
+    }
+
+    func toggleSaveRace(id: String) async {
+        guard let race = races.first(where: { $0.id == id }) else { return }
+        let newSavedState = !race.isSaved
+
+        do {
+            try await service.saveRace(id: id, isSaved: newSavedState)
+            if let index = races.firstIndex(where: { $0.id == id }) {
+                races[index].isSaved = newSavedState
+                objectWillChange.send()
+            }
+            if newSavedState {
+                savedRaces.append(races.first(where: { $0.id == id }) ?? race)
+            } else {
+                savedRaces.removeAll { $0.id == id }
+            }
+            objectWillChange.send()
+        } catch {
+            print("Failed to toggle save race: \(error)")
+        }
+    }
+
+    func registerForRace(id: String) async {
+        do {
+            try await service.registerForRace(id: id)
+            if let index = races.firstIndex(where: { $0.id == id }) {
+                races[index].isRegistered = true
+                objectWillChange.send()
+            }
+        } catch {
+            print("Failed to register for race: \(error)")
+        }
+    }
+
+    func fetchSavedRaces() async {
+        isLoading = true
+        error = nil
+        defer { isLoading = false }
+
+        do {
+            savedRaces = try await service.listRaces(filter: RaceFilter(limit: 50, offset: 0))
+                .filter { $0.isSaved }
+        } catch let error as RaceError {
+            self.error = error
+        } catch {
+            print("Failed to fetch saved races: \(error)")
+        }
+    }
+
+    var upcomingRaces: [Race] {
+        races.filter { $0.isUpcoming }.sorted { $0.raceDate < $1.raceDate }
+    }
+
+    var raceTypes: [RaceType] { RaceType.allCases }
+    var terrainTypes: [TerrainType] { TerrainType.allCases }
+}