feat(store): add In-App Purchase system with Pro subscription

Implement freemium model with StoreKit 2:
- StoreManager singleton for purchase/restore/entitlements
- ProFeature enum defining gated features
- PaywallView and OnboardingPaywallView for upsell UI
- ProGate view modifier and ProBadge component

Feature gating:
- Trip saving: 1 free trip, then requires Pro
- PDF export: Pro only with badge indicator
- Progress tab: Shows ProLockedView for free users
- Settings: Subscription management section

Also fixes pre-existing test issues with StadiumVisit
and ItineraryOption model signature changes.

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

SportsTimeTests/TripOptionsGroupingTests.swift

@@ -4,29 +4,36 @@
 //
 
 import Testing
+import Foundation
+import CoreLocation
 @testable import SportsTime
 
 struct TripOptionsGroupingTests {
 
+    // Helper to create mock ItineraryStop
+    private func makeStop(city: String, games: [String] = []) -> ItineraryStop {
+        ItineraryStop(
+            city: city,
+            state: "XX",
+            coordinate: CLLocationCoordinate2D(latitude: 0, longitude: 0),
+            games: games,
+            arrivalDate: Date(),
+            departureDate: Date(),
+            location: LocationInput(name: city, coordinate: nil),
+            firstGameStart: nil
+        )
+    }
+
     // Helper to create mock ItineraryOption
     private func makeOption(stops: [(city: String, games: [String])], totalMiles: Double = 500) -> ItineraryOption {
-        let tripStops = stops.map { stopData in
-            TripStop(
-                city: stopData.city,
-                state: "XX",
-                coordinate: .init(latitude: 0, longitude: 0),
-                games: stopData.games,
-                arrivalDate: Date(),
-                departureDate: Date(),
-                travelFromPrevious: nil
-            )
-        }
+        let itineraryStops = stops.map { makeStop(city: $0.city, games: $0.games) }
         return ItineraryOption(
-            id: UUID().uuidString,
-            stops: tripStops,
-            totalDistanceMiles: totalMiles,
+            rank: 1,
+            stops: itineraryStops,
+            travelSegments: [],
             totalDrivingHours: totalMiles / 60,
-            score: 1.0
+            totalDistanceMiles: totalMiles,
+            geographicRationale: "Test"
         )
     }