Add multi-user auth, admin panel, and timezone support; rename to Yolkbook

- Rename app from Eggtracker to Yolkbook throughout
- Add JWT-based authentication (python-jose, passlib/bcrypt)
- Add users table; all data tables gain user_id FK for full data isolation
- Super admin credentials sourced from ADMIN_USERNAME/ADMIN_PASSWORD env vars,
  synced on every startup; orphaned rows auto-assigned to admin post-migration
- Login page with self-registration; JWT stored in localStorage (30-day expiry)
- Admin panel (/admin): list users, reset passwords, disable/enable, delete,
  and impersonate (Login As) with Return to Admin banner
- Settings modal (gear icon in nav): timezone selector and change password
- Timezone stored per-user; stats date windows computed in user's timezone;
  date input setToday() respects user timezone via Intl API
- migrate_v2.sql for existing single-user installs
- Auto-migration adds timezone column to users on startup
- Updated README with full setup, auth, admin, and migration docs

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

docker-compose.yml

@@ -28,7 +28,10 @@ services:
     restart: unless-stopped
     env_file: .env
     environment:
-      DATABASE_URL: mysql+pymysql://${MYSQL_USER}:${MYSQL_PASSWORD}@db/${MYSQL_DATABASE}
+      DATABASE_URL:     mysql+pymysql://${MYSQL_USER}:${MYSQL_PASSWORD}@db/${MYSQL_DATABASE}
+      ADMIN_USERNAME:   ${ADMIN_USERNAME}
+      ADMIN_PASSWORD:   ${ADMIN_PASSWORD}
+      JWT_SECRET:       ${JWT_SECRET}
     depends_on:
       db:
         condition: service_healthy   # wait for MySQL to be ready before starting