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/ReflectApp.swift

@@ -36,6 +36,10 @@ struct ReflectApp: App {
             guard let processingTask = task as? BGProcessingTask else { return }
             BGTask.runFillInMissingDatesTask(task: processingTask)
         }
+        BGTaskScheduler.shared.register(forTaskWithIdentifier: BGTask.weatherRetryID, using: nil) { task in
+            guard let processingTask = task as? BGProcessingTask else { return }
+            BGTask.runWeatherRetryTask(task: processingTask)
+        }
         UNUserNotificationCenter.current().setBadgeCount(0)
 
         // Reset tips session on app launch