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/Planning/Engine/ScenarioAPlanner.swift

@@ -298,7 +298,7 @@ final class ScenarioAPlanner: ScenarioPlanner {
     ///
     private func buildStops(
         from games: [Game],
-        stadiums: [UUID: Stadium]
+        stadiums: [String: Stadium]
     ) -> [ItineraryStop] {
         guard !games.isEmpty else { return [] }
 
@@ -308,7 +308,7 @@ final class ScenarioAPlanner: ScenarioPlanner {
         // Group consecutive games at the same stadium into stops
         // If you visit A, then B, then A again, that's 3 stops (A, B, A)
         var stops: [ItineraryStop] = []
-        var currentStadiumId: UUID? = nil
+        var currentStadiumId: String? = nil
         var currentGames: [Game] = []
 
         for game in sortedGames {
@@ -340,8 +340,8 @@ final class ScenarioAPlanner: ScenarioPlanner {
     /// Creates an ItineraryStop from a group of games at the same stadium.
     private func createStop(
         from games: [Game],
-        stadiumId: UUID,
-        stadiums: [UUID: Stadium]
+        stadiumId: String,
+        stadiums: [String: Stadium]
     ) -> ItineraryStop? {
         guard !games.isEmpty else { return nil }
 
@@ -380,7 +380,7 @@ final class ScenarioAPlanner: ScenarioPlanner {
         var unique: [[Game]] = []
 
         for route in routes {
-            let key = route.map { $0.id.uuidString }.sorted().joined(separator: "-")
+            let key = route.map { $0.id }.sorted().joined(separator: "-")
             if !seen.contains(key) {
                 seen.insert(key)
                 unique.append(route)
@@ -396,7 +396,7 @@ final class ScenarioAPlanner: ScenarioPlanner {
     /// This ensures we get diverse options from East, Central, and West coasts.
     private func findRoutesPerRegion(
         games: [Game],
-        stadiums: [UUID: Stadium],
+        stadiums: [String: Stadium],
         allowRepeatCities: Bool
     ) -> [[Game]] {
         // Partition games by region