Add weather feature with WeatherKit integration for mood entries

Fetch and display weather data (temp, condition, hi/lo, humidity) when
users log a mood. Weather is stored as JSON on MoodEntryModel and shown
as a card in EntryDetailView. Premium-gated with location permission
prompt. Includes BGTask retry for failed fetches and full analytics.

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

Shared/Analytics.swift

@@ -451,6 +451,11 @@ extension AnalyticsManager {
         case healthKitNotAuthorized
         case healthKitSyncCompleted(total: Int, success: Int, failed: Int)
 
+        // MARK: Weather
+        case weatherToggled(enabled: Bool)
+        case weatherFetched
+        case weatherFetchFailed(error: String)
+
         // MARK: Navigation
         case tabSwitched(tab: String)
         case viewHeaderChanged(header: String)
@@ -604,6 +609,14 @@ extension AnalyticsManager {
             case .healthKitSyncCompleted(let total, let success, let failed):
                 return ("healthkit_sync_completed", ["total": total, "success": success, "failed": failed])
 
+            // Weather
+            case .weatherToggled(let enabled):
+                return ("weather_toggled", ["enabled": enabled])
+            case .weatherFetched:
+                return ("weather_fetched", nil)
+            case .weatherFetchFailed(let error):
+                return ("weather_fetch_failed", ["error": error])
+
             // Navigation
             case .tabSwitched(let tab):
                 return ("tab_switched", ["tab": tab])