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>

composeApp/src/commonMain/kotlin/com/example/casera/utils/SubscriptionHelper.kt

@@ -45,12 +45,13 @@ object SubscriptionHelper {
 
     /**
      * Derive the current subscription tier from DataManager.
-     * "pro" if the backend subscription has a non-empty expiresAt (active paid plan),
+     * "pro" if the backend subscription has an active trial or a non-empty expiresAt (active paid plan),
      * "free" otherwise.
      */
     val currentTier: String
         get() {
             val subscription = DataManager.subscription.value ?: return "free"
+            if (subscription.trialActive) return "pro"
             val expiresAt = subscription.expiresAt
             return if (!expiresAt.isNullOrEmpty()) "pro" else "free"
         }
@@ -68,6 +69,25 @@ object SubscriptionHelper {
             return currentTier == "pro"
         }
 
+    /**
+     * Check if the user can purchase a subscription on the given platform.
+     * If the user already has an active Pro subscription from a different platform,
+     * purchasing on this platform is not allowed.
+     *
+     * @param currentPlatform The platform attempting the purchase ("ios", "android", or "stripe")
+     * @return UsageCheck with allowed=false if already subscribed on another platform
+     */
+    fun canPurchaseOnPlatform(currentPlatform: String): UsageCheck {
+        val subscription = DataManager.subscription.value
+            ?: return UsageCheck(allowed = true, triggerKey = null)
+        if (currentTier != "pro") return UsageCheck(allowed = true, triggerKey = null)
+        val source = subscription.subscriptionSource
+        if (source != null && source != currentPlatform) {
+            return UsageCheck(allowed = false, triggerKey = "already_subscribed_other_platform")
+        }
+        return UsageCheck(allowed = true, triggerKey = null)
+    }
+
     // ===== PROPERTY (RESIDENCE) =====
 
     /**