refactor: change domain model IDs from UUID to String canonical IDs

This refactor fixes the achievement system by using stable canonical string
IDs (e.g., "stadium_mlb_fenway_park") instead of random UUIDs. This ensures
stadium mappings for achievements are consistent across app launches and
CloudKit sync operations.

Changes:
- Stadium, Team, Game: id property changed from UUID to String
- Trip, TripStop, TripPreferences: updated to use String IDs for games/stadiums
- CKModels: removed UUID parsing, use canonical IDs directly
- AchievementEngine: now matches against canonical stadium IDs
- All test files updated to use String IDs instead of UUID()

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

SportsTime/Features/Trip/Views/TripCreationView.swift

@@ -926,7 +926,7 @@ struct TripCreationView: View {
         )
     }
 
-    private func buildGamesDictionary() -> [UUID: RichGame] {
+    private func buildGamesDictionary() -> [String: RichGame] {
         viewModel.availableGames.reduce(into: [:]) { $0[$1.id] = $1 }
     }
 }
@@ -949,16 +949,16 @@ extension TripCreationViewModel.ViewState {
 
 struct GamePickerSheet: View {
     let games: [RichGame]
-    @Binding var selectedIds: Set<UUID>
+    @Binding var selectedIds: Set<String>
     @Environment(\.dismiss) private var dismiss
     @Environment(\.colorScheme) private var colorScheme
 
     @State private var expandedSports: Set<Sport> = []
-    @State private var expandedTeams: Set<UUID> = []
+    @State private var expandedTeams: Set<String> = []
 
     // Group games by Sport → Team (home team only to avoid duplicates)
     private var gamesBySport: [Sport: [TeamWithGames]] {
-        var result: [Sport: [UUID: TeamWithGames]] = [:]
+        var result: [Sport: [String: TeamWithGames]] = [:]
 
         for game in games {
             let sport = game.game.sport
@@ -1063,9 +1063,9 @@ struct GamePickerSheet: View {
 struct SportSection: View {
     let sport: Sport
     let teams: [TeamWithGames]
-    @Binding var selectedIds: Set<UUID>
+    @Binding var selectedIds: Set<String>
     @Binding var expandedSports: Set<Sport>
-    @Binding var expandedTeams: Set<UUID>
+    @Binding var expandedTeams: Set<String>
     let selectedCount: Int
 
     @Environment(\.colorScheme) private var colorScheme
@@ -1146,8 +1146,8 @@ struct SportSection: View {
 
 struct TeamSection: View {
     let teamData: TeamWithGames
-    @Binding var selectedIds: Set<UUID>
-    @Binding var expandedTeams: Set<UUID>
+    @Binding var selectedIds: Set<String>
+    @Binding var expandedTeams: Set<String>
 
     @Environment(\.colorScheme) private var colorScheme
 
@@ -1310,7 +1310,7 @@ struct TeamWithGames: Identifiable {
     let sport: Sport
     var games: [RichGame]
 
-    var id: UUID { team.id }
+    var id: String { team.id }
 
     var sortedGames: [RichGame] {
         games.sorted { $0.game.dateTime < $1.game.dateTime }
@@ -1504,7 +1504,7 @@ enum CitiesFilter: Int, CaseIterable, Identifiable {
 
 struct TripOptionsView: View {
     let options: [ItineraryOption]
-    let games: [UUID: RichGame]
+    let games: [String: RichGame]
     let preferences: TripPreferences?
     let convertToTrip: (ItineraryOption) -> Trip
 
@@ -1774,7 +1774,7 @@ struct TripOptionsView: View {
 
 struct TripOptionCard: View {
     let option: ItineraryOption
-    let games: [UUID: RichGame]
+    let games: [String: RichGame]
     let onSelect: () -> Void
     @Environment(\.colorScheme) private var colorScheme
 
@@ -2393,7 +2393,7 @@ struct DayCell: View {
 // MARK: - Team Picker Sheet
 
 struct TeamPickerSheet: View {
-    @Binding var selectedTeamId: UUID?
+    @Binding var selectedTeamId: String?
     let teamsBySport: [Sport: [Team]]
 
     @Environment(\.dismiss) private var dismiss