refactor: split backend into standalone server project

Remove embedded frontend and workflow editor assets, add standalone API deployment configuration, and retain the current backend service updates.

docker-compose.lancedb.yml

@@ -1,24 +1,4 @@
 services:
-  mysql:
-    image: mysql:8.4
-    restart: unless-stopped
-    environment:
-      MYSQL_DATABASE: cs_ai_agent
-      MYSQL_USER: cs_ai_agent
-      MYSQL_PASSWORD: cs_ai_agent_password
-      MYSQL_ROOT_PASSWORD: cs_ai_agent_root_password
-      TZ: Asia/Shanghai
-    command:
-      - --character-set-server=utf8mb4
-      - --collation-server=utf8mb4_unicode_ci
-    volumes:
-      - mysql-data:/var/lib/mysql
-    healthcheck:
-      test: ["CMD-SHELL", "mysqladmin ping -h 127.0.0.1 -u\"$${MYSQL_USER}\" -p\"$${MYSQL_PASSWORD}\" --silent"]
-      interval: 10s
-      timeout: 5s
-      retries: 10
-
   agent-desk:
     build:
       context: .
@@ -28,9 +8,6 @@ services:
         LANCEDB_VERSION: v0.1.2
     image: mlogclub/agent-desk:latest-lancedb
     restart: unless-stopped
-    depends_on:
-      mysql:
-        condition: service_healthy
     ports:
       - "8083:8083"
     volumes:
@@ -38,7 +15,8 @@ services:
       - ./docker/agent-desk-lancedb.yaml:/app/config/config.yaml:ro
     environment:
       TZ: Asia/Shanghai
+      AGENT_DESK_DB_TYPE: postgres
+      AGENT_DESK_DB_DSN: ${AGENT_DESK_DB_DSN:-host=host.docker.internal user=cs_ai_agent password=cs_ai_agent_password dbname=cs_ai_agent port=5432 sslmode=disable TimeZone=Asia/Shanghai}
 
 volumes:
-  mysql-data:
   agent-desk-data: