Add task completion animations, subscription trials, and quiet debug console

- Completion animations: play user-selected animation on task card after completing,
  with DataManager guard to prevent race condition during animation playback.
  Works in both AllTasksView and ResidenceDetailView. Animation preference
  persisted via @AppStorage and configurable from Settings.
- Subscription: add trial fields (trialStart, trialEnd, trialActive) and
  subscriptionSource to model, cross-platform purchase guard, trial banner
  in upgrade prompt, and platform-aware subscription management in profile.
- Analytics: disable PostHog SDK debug logging and remove console print
  statements to reduce debug console noise.
- Documents: remove redundant nested do-catch blocks in ViewModel wrapper.
- Widgets: add debounced timeline reloads and thread-safe file I/O queue.
- Onboarding: fix animation leak on disappear, remove unused state vars.
- Remove unused files (ContentView, StateFlowExtensions, CustomView).

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

iosApp/CaseraTests/SubscriptionGatingTests.swift

@@ -45,8 +45,9 @@ private let proLimits = TierLimits(
     documents: nil
 )
 
-// MARK: - Serialized Suite (SubscriptionCacheWrapper is a shared singleton)
+// MARK: - Serialized Suite (SubscriptionCacheWrapper is a @MainActor shared singleton)
 
+@MainActor
 @Suite(.serialized)
 struct SubscriptionGatingTests {