Add Garmin Connect auto-sync via python-garminconnect

- GarminConnectConfig model stores encrypted credentials and OAuth token
- garmin_connect_sync service: token-based auth with password fallback,
  activity FIT download + queue, daily wellness from JSON API
- Celery beat schedule: sync_all_garmin_connect fires every hour
- New API router /api/garmin-sync: config CRUD, manual trigger
- Beat container added to docker-compose.yml and docker-compose.deploy.yml
- ProfilePage: Garmin Connect section with connect/update/disconnect and Sync now

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -83,6 +83,26 @@ services:
       redis:
         condition: service_healthy
 
+  beat:
+    build:
+      context: ./backend
+      dockerfile: Dockerfile.worker
+    container_name: milevault_beat
+    restart: unless-stopped
+    command: celery -A app.workers.celery_app beat --loglevel=info
+    environment:
+      DATABASE_URL: postgresql+asyncpg://${DB_USER:-milevault}:${DB_PASSWORD:-milevault}@db:5432/milevault
+      REDIS_URL: redis://:${REDIS_PASSWORD:-milevault}@redis:6379/0
+      SECRET_KEY: ${SECRET_KEY:-changeme_please_set_in_env_file_32chars}
+      FILE_STORE_PATH: /data/files
+    volumes:
+      - file_data:/data/files
+    depends_on:
+      db:
+        condition: service_healthy
+      redis:
+        condition: service_healthy
+
   frontend:
     build:
       context: ./frontend