refactor: 将客服后端重构为宿主可嵌入模块

- 注入数据库、运行时配置、统一响应、文件存储和平台 AI 能力，补充业务读写工具与客户快捷操作契约。

- 移除模块内重复的组织、客户、工单、标签、技能、旧工作流、MCP 和迁移实现，将身份权限与业务主体交由宿主管理。

- 使用 libSQL 重构向量存储，并完善图片消息、访客身份、排队调度、企业微信和支持聊天页面。

- 统一 HTTP、DTO 与 WebSocket 的 snake_case 协议，补齐模块初始化、业务动作和公共载荷等回归测试。

config/config.example.yaml

@@ -12,14 +12,9 @@ server:
       - http://localhost:3000
 
 db:
-  # Database driver. Supported values: sqlite, mysql, postgres (postgresql is also accepted).
-  type: sqlite
-  # Database connection string.
-  # SQLite example: file:./data/app.db?_busy_timeout=5000
-  # MySQL example: user:password@tcp(127.0.0.1:3306)/cs_ai_agent_db?charset=utf8mb4&parseTime=True&multiStatements=true&loc=Local
-  # For MySQL, keep parseTime=True so datetime fields are scanned into Go time values correctly.
-  # PostgreSQL example: host=127.0.0.1 user=cs_ai_agent password=change-me dbname=cs_ai_agent port=5432 sslmode=disable TimeZone=Asia/Shanghai
-  dsn: file:./data/app.db?_busy_timeout=5000
+  # PostgreSQL is the only supported business database.
+  type: postgres
+  dsn: host=127.0.0.1 user=kefu password=change-me dbname=kefu port=5432 sslmode=disable TimeZone=Asia/Shanghai
   # Maximum number of idle connections kept in the pool. Values <= 0 use the database/sql default.
   maxIdleConns: 5
   # Maximum number of open connections. Values <= 0 mean no explicit limit.
@@ -63,31 +58,8 @@ storage:
     signedUrlExpireSeconds: 600
 
 vectorDB:
-  type: qdrant # qdrant, lancedb
-  qdrant:
-    host: 127.0.0.1
-    grpcPort: 6334
-    apiKey: ""
-    useTls: false
-  # LanceDB requires building the backend with -tags lancedb and LanceDB native libraries.
-  lancedb:
-    path: data/lancedb
-
-mcp:
-  # Global switch for MCP tool integration.
-  # When false, MCP tool catalog, debug endpoints, and runtime tool calls are disabled.
-  enabled: true
-  # MCP server registry. Each map key is the serverCode used by toolCode values like "system/tool_name".
-  servers:
-    system:
-      # Whether this MCP server is available for catalog listing, debug calls, and agent runtime calls.
-      enabled: true
-      # Streamable HTTP MCP endpoint. The built-in system server is exposed by this backend at /api/mcp.
-      endpoint: "http://127.0.0.1:8083/api/mcp"
-      # Connection and request timeout in milliseconds. Values <= 0 fall back to 15000.
-      timeoutMs: 15000
-      # Extra HTTP headers sent to this MCP server on every request, for example Authorization or tenant headers.
-      headers: {}
+  # Local libSQL file used only for RAG embeddings and knowledge text chunks.
+  path: data/agent/vectors.db
 
 wxWork:
   # Whether to enable WeCom features.