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/Models/UserDefaultsStore.swift

@@ -207,6 +207,7 @@ class UserDefaultsStore {
         case lockScreenStyle
         case celebrationAnimation
         case hapticFeedbackEnabled
+        case weatherEnabled
 
         case contentViewCurrentSelectedHeaderViewBackDays
         case contentViewHeaderTag