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/Features/Progress/VisitListTests.swift

@@ -29,24 +29,27 @@ final class VisitListTests: XCTestCase {
             stadiumId: stadiumId,
             stadiumNameAtVisit: "Yankee Stadium",
             visitDate: Date().addingTimeInterval(-86400 * 30), // 30 days ago
+            sport: .mlb,
             visitType: .game,
-            dataSource: .manual
+            dataSource: .fullyManual
         )
 
         let visit2 = StadiumVisit(
             stadiumId: stadiumId,
             stadiumNameAtVisit: "Yankee Stadium",
             visitDate: Date().addingTimeInterval(-86400 * 7), // 7 days ago
+            sport: .mlb,
             visitType: .game,
-            dataSource: .manual
+            dataSource: .fullyManual
         )
 
         let visit3 = StadiumVisit(
             stadiumId: stadiumId,
             stadiumNameAtVisit: "Yankee Stadium",
             visitDate: Date(), // today
+            sport: .mlb,
             visitType: .tour,
-            dataSource: .manual
+            dataSource: .fullyManual
         )
 
         modelContext.insert(visit1)
@@ -77,8 +80,9 @@ final class VisitListTests: XCTestCase {
                 stadiumId: stadium1,
                 stadiumNameAtVisit: "Yankee Stadium",
                 visitDate: Date().addingTimeInterval(Double(-i * 86400)),
+                sport: .mlb,
                 visitType: .game,
-                dataSource: .manual
+                dataSource: .fullyManual
             )
             modelContext.insert(visit)
         }
@@ -87,8 +91,9 @@ final class VisitListTests: XCTestCase {
             stadiumId: stadium2,
             stadiumNameAtVisit: "Fenway Park",
             visitDate: Date(),
+            sport: .mlb,
             visitType: .game,
-            dataSource: .manual
+            dataSource: .fullyManual
         )
         modelContext.insert(fenwayVisit)
         try modelContext.save()