feat(api,web): auth et first-run — bootstrap admin, login, session, gardes

- api: auth controller/service, config env
- web: App/LoginPage/ProfilePage, garde d'auth, client API, styles
- shared: types/contrats auth
- compose: variables d'environnement first-run

Refs: #14

docker-compose.yaml

@@ -11,6 +11,8 @@ services:
       STORAGE_DIR: /data/storage
       JWT_SECRET: ${JWT_SECRET:-dev-change-me-readabook}
       OPEN_LIBRARY_ENABLED: ${OPEN_LIBRARY_ENABLED:-true}
+      INITIAL_ADMIN_EMAIL: ${INITIAL_ADMIN_EMAIL:-admin@readabook.local}
+      INITIAL_ADMIN_PASSWORD: ${INITIAL_ADMIN_PASSWORD:-readabook-admin-change-me}
     volumes:
       - ./data:/data
       - ./data/library:/library:ro