feat: add PostHog analytics with full event tracking across app

Integrate self-hosted PostHog (SPM) with AnalyticsManager singleton wrapping
all SDK calls. Adds ~40 type-safe events covering trip planning, schedule,
progress, IAP, settings, polls, export, and share flows. Includes session
replay, autocapture, network telemetry, privacy opt-out toggle in Settings,
and super properties (app version, device, pro status, selected sports).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

SportsTime/Features/Polls/ViewModels/PollVotingViewModel.swift

@@ -52,6 +52,7 @@ final class PollVotingViewModel {
 
             _ = try await pollService.submitVote(vote)
             didSubmit = true
+            AnalyticsManager.shared.track(.pollVoted(pollId: pollId.uuidString))
         } catch let pollError as PollError {
             error = pollError
         } catch {