Add featured trips carousel on home screen

- Generate 8 suggested trips on app launch (2 per region: East, Central, West, Cross-Country)
- Each region has single-sport and multi-sport trip options
- Region classification based on stadium longitude
- Animated loading state with shimmer placeholders
- Loading messages use Foundation Models when available, fallback otherwise
- Tap card to view trip details in sheet
- Refresh button to regenerate trips
- Fixed-height cards with aligned top/bottom layout

New files:
- Region.swift: Geographic region enum with longitude classification
- LoadingTextGenerator.swift: On-device AI loading messages
- SuggestedTripsGenerator.swift: Trip generation service
- SuggestedTripCard.swift: Carousel card component
- LoadingTripsView.swift: Animated loading state

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

SportsTime/Core/Models/Domain/Region.swift

@@ -0,0 +1,54 @@
+//
+//  Region.swift
+//  SportsTime
+//
+//  Geographic regions for trip classification.
+//
+
+import Foundation
+
+enum Region: String, CaseIterable, Identifiable {
+    case east = "East Coast"
+    case central = "Central"
+    case west = "West Coast"
+    case crossCountry = "Cross-Country"
+
+    var id: String { rawValue }
+
+    var displayName: String { rawValue }
+
+    var shortName: String {
+        switch self {
+        case .east: return "East"
+        case .central: return "Central"
+        case .west: return "West"
+        case .crossCountry: return "Coast to Coast"
+        }
+    }
+
+    var iconName: String {
+        switch self {
+        case .east: return "building.2"
+        case .central: return "building"
+        case .west: return "sun.max"
+        case .crossCountry: return "arrow.left.arrow.right"
+        }
+    }
+
+    /// Classifies a stadium's region based on longitude.
+    ///
+    /// Longitude boundaries:
+    /// - East: > -85 (NYC, Boston, Miami, Toronto, Montreal, Atlanta)
+    /// - Central: -110 to -85 (Chicago, Houston, Dallas, Minneapolis, Denver)
+    /// - West: < -110 (LA, SF, Seattle, Phoenix, Las Vegas)
+    static func classify(longitude: Double) -> Region {
+        switch longitude {
+        case _ where longitude > -85:
+            return .east
+        case -110...(-85):
+            return .central
+        default:
+            return .west
+        }
+    }
+}

SportsTime/Core/Models/Domain/Stadium.swift

@@ -51,6 +51,10 @@ struct Stadium: Identifiable, Codable, Hashable {
         "\(city), \(state)"
     }
 
+    var region: Region {
+        Region.classify(longitude: longitude)
+    }
+
     func distance(to other: Stadium) -> CLLocationDistance {
         location.distance(from: other.location)
     }