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/Core/Services/GameMatcher.swift

@@ -43,7 +43,7 @@ enum NoMatchReason: Sendable {
 // MARK: - Game Match Result
 
 struct GameMatchCandidate: Identifiable, Sendable {
-    let id: UUID
+    let id: String
     let game: Game
     let stadium: Stadium
     let homeTeam: Team
@@ -67,14 +67,20 @@ struct GameMatchCandidate: Identifiable, Sendable {
 
     /// Initialize from a scraped historical game
     init(scrapedGame: ScrapedGame, stadium: Stadium) {
-        self.id = UUID()
+        let matchId = UUID()
+        self.id = "scraped_match_\(matchId.uuidString)"
         self.stadium = stadium
 
+        // Generate synthetic IDs for scraped games
+        let syntheticHomeTeamId = "scraped_team_\(UUID().uuidString)"
+        let syntheticAwayTeamId = "scraped_team_\(UUID().uuidString)"
+        let syntheticGameId = "scraped_game_\(matchId.uuidString)"
+
         // Create synthetic Team objects from scraped names
         // Scraped names already include city (e.g., "Chicago Cubs"), so we use empty city
         // to avoid duplication in fullName computed property
         self.homeTeam = Team(
-            id: UUID(),
+            id: syntheticHomeTeamId,
             name: scrapedGame.homeTeam,
             abbreviation: String(scrapedGame.homeTeam.suffix(3)).uppercased(),
             sport: scrapedGame.sport,
@@ -83,7 +89,7 @@ struct GameMatchCandidate: Identifiable, Sendable {
         )
 
         self.awayTeam = Team(
-            id: UUID(),
+            id: syntheticAwayTeamId,
             name: scrapedGame.awayTeam,
             abbreviation: String(scrapedGame.awayTeam.suffix(3)).uppercased(),
             sport: scrapedGame.sport,
@@ -94,7 +100,7 @@ struct GameMatchCandidate: Identifiable, Sendable {
         // Create synthetic Game object
         let year = Calendar.current.component(.year, from: scrapedGame.date)
         self.game = Game(
-            id: self.id,
+            id: syntheticGameId,
             homeTeamId: self.homeTeam.id,
             awayTeamId: self.awayTeam.id,
             stadiumId: stadium.id,