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。

internal/pkg/utils/message_test.go

@@ -23,14 +23,14 @@ func TestBuildIMMessageAssetPayloadForResponseAddsSignedURL(t *testing.T) {
 		},
 	})
 
-	payload := `{"assetId":"asset_1","provider":"local","storageKey":"attachments/demo.png","filename":"demo.png"}`
+	payload := `{"asset_id":"asset_1","provider":"local","storage_key":"attachments/demo.png","filename":"demo.png"}`
 	got := buildIMMessageAssetPayloadForResponse(payload)
 
 	if !strings.Contains(got, `"provider":"local"`) {
 		t.Fatalf("expected provider in payload, got: %s", got)
 	}
-	if !strings.Contains(got, `"storageKey":"attachments/demo.png"`) {
-		t.Fatalf("expected storageKey in payload, got: %s", got)
+	if !strings.Contains(got, `"storage_key":"attachments/demo.png"`) {
+		t.Fatalf("expected storage_key in payload, got: %s", got)
 	}
 	if !strings.Contains(got, `"url":"https://files.example.com/attachments/demo.png"`) {
 		t.Fatalf("expected signed url in payload, got: %s", got)
@@ -99,7 +99,7 @@ func TestBuildRenderableMessageTransformsPayloadAndHTML(t *testing.T) {
 
 	image := &models.Message{
 		MessageType: enums.IMMessageTypeImage,
-		Payload:     `{"assetId":"asset_1","provider":"local","storageKey":"attachments/demo.png","filename":"demo.png"}`,
+		Payload:     `{"asset_id":"asset_1","provider":"local","storage_key":"attachments/demo.png","filename":"demo.png"}`,
 	}
 	_, imagePayload := BuildRenderableMessage(image)
 	if !strings.Contains(imagePayload, `"url":"https://files.example.com/attachments/demo.png"`) {