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/TimelineItemView.swift

@@ -13,13 +13,13 @@ import SwiftUI
 /// Renders a single timeline item (stop, travel, or rest).
 struct TimelineItemView: View {
     let item: TimelineItem
-    let games: [UUID: RichGame]
+    let games: [String: RichGame]
     let isFirst: Bool
     let isLast: Bool
 
     init(
         item: TimelineItem,
-        games: [UUID: RichGame],
+        games: [String: RichGame],
         isFirst: Bool = false,
         isLast: Bool = false
     ) {
@@ -122,7 +122,7 @@ struct TimelineItemView: View {
 
 struct StopItemContent: View {
     let stop: ItineraryStop
-    let games: [UUID: RichGame]
+    let games: [String: RichGame]
 
     private var gamesAtStop: [RichGame] {
         stop.games.compactMap { games[$0] }
@@ -291,7 +291,7 @@ struct TimelineGameRow: View {
 /// Full timeline view for an itinerary option.
 struct TimelineView: View {
     let option: ItineraryOption
-    let games: [UUID: RichGame]
+    let games: [String: RichGame]
 
     private var timeline: [TimelineItem] {
         option.generateTimeline()
@@ -316,7 +316,7 @@ struct TimelineView: View {
 /// Horizontal scrolling timeline for compact display.
 struct HorizontalTimelineView: View {
     let option: ItineraryOption
-    let games: [UUID: RichGame]
+    let games: [String: RichGame]
 
     private var timeline: [TimelineItem] {
         option.generateTimeline()
@@ -368,7 +368,7 @@ struct HorizontalTimelineView: View {
 
 struct HorizontalTimelineItemView: View {
     let item: TimelineItem
-    let games: [UUID: RichGame]
+    let games: [String: RichGame]
 
     var body: some View {
         VStack(spacing: 4) {