feat: iOS widgets + fix sleep showing yesterday's data

Widgets:
- HabitsProgressWidget (small/medium): progress ring, completed/total habits, tasks count
- HealthSummaryWidget (small/medium): readiness score, steps, sleep, heart rate
- Shared Keychain access group for app ↔ widget token sharing
- Widget data refreshes every 30 minutes

Sleep fix:
- Changed sleep window from "24 hours back" to "6 PM yesterday → now"
- Captures overnight sleep correctly without showing previous day's data
- Applied to both fetchSleepData (sync) and fetchSleepSegments (detail view)

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

project.yml

@@ -10,6 +10,8 @@ targets:
     sources: PulseHealth
     entitlements:
       path: PulseHealth/PulseHealth.entitlements
+    dependencies:
+      - target: PulseWidgetExtension
     settings:
       base:
         PRODUCT_BUNDLE_IDENTIFIER: com.daniil.pulsehealth
@@ -23,3 +25,23 @@ targets:
       BackgroundModes:
         modes:
           - processing
+
+  PulseWidgetExtension:
+    type: app-extension
+    platform: iOS
+    sources: PulseWidget
+    entitlements:
+      path: PulseWidget/PulseWidget.entitlements
+    settings:
+      base:
+        PRODUCT_BUNDLE_IDENTIFIER: com.daniil.pulsehealth.widget
+        SWIFT_VERSION: 5.9
+        CODE_SIGN_STYLE: Automatic
+        DEVELOPMENT_TEAM: V9AG8JTFLC
+        INFOPLIST_FILE: ""
+    info:
+      path: PulseWidget/Info.plist
+      properties:
+        CFBundleDisplayName: Pulse Widget
+        NSExtension:
+          NSExtensionPointIdentifier: com.apple.widgetkit-extension