feat(polls): add DeepLinkHandler and test mock helpers

- Extract deep link handling into dedicated DeepLinkHandler service
- Add MockData+Polls.swift with reusable test mocks for Trip, TripStop,
  TripPoll, PollVote, and PollResults
- Update SportsTimeApp to use DeepLinkHandler.shared
- Add error alert for deep link failures

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

SportsTimeTests/Mocks/MockData+Polls.swift

@@ -0,0 +1,130 @@
+//
+//  MockData+Polls.swift
+//  SportsTimeTests
+//
+//  Mock data extensions for poll-related tests
+//
+
+import Foundation
+@testable import SportsTime
+
+// MARK: - Trip Mock
+
+extension Trip {
+    /// Creates a mock trip for testing
+    static func mock(
+        id: UUID = UUID(),
+        name: String = "Test Trip",
+        cities: [String] = ["Boston", "New York"],
+        startDate: Date = Date(),
+        games: [String] = []
+    ) -> Trip {
+        let stops = cities.enumerated().map { index, city in
+            TripStop.mock(
+                stopNumber: index + 1,
+                city: city,
+                arrivalDate: startDate.addingTimeInterval(Double(index) * 86400),
+                departureDate: startDate.addingTimeInterval(Double(index + 1) * 86400),
+                games: games
+            )
+        }
+
+        return Trip(
+            id: id,
+            name: name,
+            preferences: TripPreferences(
+                planningMode: .dateRange,
+                sports: [.mlb],
+                startDate: startDate,
+                endDate: startDate.addingTimeInterval(86400 * Double(cities.count))
+            ),
+            stops: stops
+        )
+    }
+}
+
+// MARK: - TripStop Mock
+
+extension TripStop {
+    /// Creates a mock trip stop for testing
+    static func mock(
+        stopNumber: Int = 1,
+        city: String = "Boston",
+        state: String = "MA",
+        arrivalDate: Date = Date(),
+        departureDate: Date? = nil,
+        games: [String] = []
+    ) -> TripStop {
+        TripStop(
+            stopNumber: stopNumber,
+            city: city,
+            state: state,
+            arrivalDate: arrivalDate,
+            departureDate: departureDate ?? arrivalDate.addingTimeInterval(86400),
+            games: games
+        )
+    }
+}
+
+// MARK: - TripPoll Mock
+
+extension TripPoll {
+    /// Creates a mock poll for testing
+    static func mock(
+        id: UUID = UUID(),
+        title: String = "Test Poll",
+        ownerId: String = "mockOwner",
+        shareCode: String? = nil,
+        tripCount: Int = 2,
+        trips: [Trip]? = nil
+    ) -> TripPoll {
+        let tripSnapshots = trips ?? (0..<tripCount).map { index in
+            Trip.mock(name: "Trip \(index + 1)", cities: ["City\(index)A", "City\(index)B"])
+        }
+
+        return TripPoll(
+            id: id,
+            title: title,
+            ownerId: ownerId,
+            shareCode: shareCode ?? TripPoll.generateShareCode(),
+            tripSnapshots: tripSnapshots
+        )
+    }
+}
+
+// MARK: - PollVote Mock
+
+extension PollVote {
+    /// Creates a mock vote for testing
+    static func mock(
+        id: UUID = UUID(),
+        pollId: UUID = UUID(),
+        odg: String = "mockVoter",
+        rankings: [Int] = [0, 1]
+    ) -> PollVote {
+        PollVote(
+            id: id,
+            pollId: pollId,
+            odg: odg,
+            rankings: rankings
+        )
+    }
+}
+
+// MARK: - PollResults Mock
+
+extension PollResults {
+    /// Creates mock results for testing
+    static func mock(
+        poll: TripPoll? = nil,
+        votes: [PollVote]? = nil
+    ) -> PollResults {
+        let testPoll = poll ?? TripPoll.mock()
+        let testVotes = votes ?? [
+            PollVote.mock(pollId: testPoll.id, odg: "voter1", rankings: [0, 1]),
+            PollVote.mock(pollId: testPoll.id, odg: "voter2", rankings: [1, 0])
+        ]
+
+        return PollResults(poll: testPoll, votes: testVotes)
+    }
+}