Add AI-powered mental wellness features: Reflection Companion, Pattern Tags, Weekly Digest

Three new Foundation Models features to deepen user engagement with mental wellness:

1. AI Reflection Companion — personalized feedback after completing guided reflections,
   referencing the user's actual words with personality-pack-adapted tone
2. Mood Pattern Tags — auto-extracts theme tags (work, family, stress, etc.) from notes
   and reflections, displayed as colored pills on entries
3. Weekly Emotional Digest — BGTask-scheduled Sunday digest with headline, summary,
   highlight, and intention; shown as card in Insights tab with notification

All features: on-device (zero cost), premium-gated, iOS 26+ with graceful degradation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Shared/ReflectApp.swift

@@ -40,6 +40,10 @@ struct ReflectApp: App {
             guard let processingTask = task as? BGProcessingTask else { return }
             BGTask.runWeatherRetryTask(task: processingTask)
         }
+        BGTaskScheduler.shared.register(forTaskWithIdentifier: BGTask.weeklyDigestID, using: nil) { task in
+            guard let processingTask = task as? BGProcessingTask else { return }
+            BGTask.runWeeklyDigestTask(task: processingTask)
+        }
         UNUserNotificationCenter.current().setBadgeCount(0)
 
         // Reset tips session on app launch
@@ -98,6 +102,7 @@ struct ReflectApp: App {
         }.onChange(of: scenePhase) { _, newPhase in
             if newPhase == .background {
                 BGTask.scheduleBackgroundProcessing()
+                BGTask.scheduleWeeklyDigest()
                 WidgetCenter.shared.reloadAllTimelines()
                 // Flush pending analytics events
                 AnalyticsManager.shared.flush()