feat: implement local authentication mode and update related components

.env.example

@@ -16,6 +16,8 @@ CORS_ORIGINS=http://localhost:3000
 DB_AUTO_MIGRATE=true
 LOG_LEVEL=INFO
 REQUEST_LOG_SLOW_MS=1000
+AUTH_MODE=local
+LOCAL_AUTH_TOKEN=change-me
 
 # --- frontend settings ---
 # REQUIRED: Public URL used by the browser to reach the API.