fix: widgets use App Group shared UserDefaults instead of Keychain

- Widgets can't access app's Keychain (different sandbox)
- App writes data to shared UserDefaults (group.com.daniil.pulsehealth)
- Widgets read from shared UserDefaults — no API calls needed
- WidgetDataService: updates widget data + reloads timelines
- DashboardView: pushes habits/tasks data to widget after load
- HealthView: pushes health data to widget after load
- App Group capability added to both app and widget entitlements
- Widgets update every 15 minutes from cached data

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

project.yml

@@ -25,11 +25,16 @@ targets:
       BackgroundModes:
         modes:
           - processing
+      AppGroups:
+        groups:
+          - group.com.daniil.pulsehealth
 
   PulseWidgetExtension:
     type: app-extension
     platform: iOS
     sources: PulseWidget
+    entitlements:
+      path: PulseWidget/PulseWidget.entitlements
     settings:
       base:
         PRODUCT_BUNDLE_IDENTIFIER: com.daniil.pulsehealth.widget
@@ -40,3 +45,7 @@ targets:
         MARKETING_VERSION: "1.0"
         CURRENT_PROJECT_VERSION: "1"
         INFOPLIST_KEY_CFBundleDisplayName: Pulse Widget
+    capabilities:
+      AppGroups:
+        groups:
+          - group.com.daniil.pulsehealth