feat(polls): implement group trip polling MVP

Add complete group trip polling feature allowing users to share trips
with friends for voting using Borda count scoring.

New components:
- TripPoll and PollVote domain models with share codes and rankings
- LocalTripPoll and LocalPollVote SwiftData models for persistence
- CKTripPoll and CKPollVote CloudKit record wrappers
- PollService actor for CloudKit CRUD operations and subscriptions
- PollCreation/Detail/Voting views and view models
- Deep link handling for sportstime://poll/{code} URLs
- Debug Pro status override toggle in Settings

Integration:
- HomeView shows polls section in My Trips
- SportsTimeApp registers SwiftData models and handles deep links

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

SportsTime/SportsTimeApp.swift

@@ -35,6 +35,9 @@ struct SportsTimeApp: App {
             VisitPhotoMetadata.self,
             Achievement.self,
             CachedGameScore.self,
+            // Poll models
+            LocalTripPoll.self,
+            LocalPollVote.self,
             // Canonical data models
             SyncState.self,
             CanonicalStadium.self,
@@ -78,6 +81,7 @@ struct BootstrappedContentView: View {
     @State private var bootstrapError: Error?
     @State private var hasCompletedInitialSync = false
     @State private var showOnboardingPaywall = false
+    @State private var pollShareCode: String?
 
     private var shouldShowOnboardingPaywall: Bool {
         !UserDefaults.standard.bool(forKey: "hasSeenOnboardingPaywall") && !StoreManager.shared.isPro
@@ -99,6 +103,11 @@ struct BootstrappedContentView: View {
                         OnboardingPaywallView(isPresented: $showOnboardingPaywall)
                             .interactiveDismissDisabled()
                     }
+                    .sheet(item: $pollShareCode) { code in
+                        NavigationStack {
+                            PollDetailView(shareCode: code)
+                        }
+                    }
                     .onAppear {
                         if shouldShowOnboardingPaywall {
                             showOnboardingPaywall = true
@@ -109,6 +118,9 @@ struct BootstrappedContentView: View {
         .task {
             await performBootstrap()
         }
+        .onOpenURL { url in
+            handleDeepLink(url)
+        }
         .onChange(of: scenePhase) { _, newPhase in
             switch newPhase {
             case .active:
@@ -191,6 +203,25 @@ struct BootstrappedContentView: View {
             print("Background sync error: \(error.localizedDescription)")
         }
     }
+
+    // MARK: - Deep Link Handling
+
+    private func handleDeepLink(_ url: URL) {
+        // Handle sportstime://poll/{code} deep links
+        guard url.scheme == "sportstime",
+              url.host == "poll",
+              let code = url.pathComponents.dropFirst().first,
+              code.count == 6
+        else { return }
+
+        pollShareCode = code.uppercased()
+    }
+}
+
+// MARK: - String Identifiable for Sheet
+
+extension String: @retroactive Identifiable {
+    public var id: String { self }
 }
 
 // MARK: - Bootstrap Loading View