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/openidentity/openidentity.go

@@ -1,12 +1,17 @@
 package openidentity
 
-import "code.tczkiot.com/wlw/ai-agent/internal/pkg/enums"
+import (
+	"code.tczkiot.com/wlw/ai-agent/identity"
+	"code.tczkiot.com/wlw/ai-agent/internal/pkg/enums"
+)
 
 // ExternalUser is a be-system user identity adapted for customer-service
 // conversations. Authentication is completed by the host before this value is
 // created; this package contains no token parsing or verification.
 type ExternalUser struct {
-	ExternalSource enums.ExternalSource `json:"externalSource"`
-	ExternalID     string               `json:"externalId"`
-	ExternalName   string               `json:"externalName"`
+	ExternalSource enums.ExternalSource `json:"external_source"`
+	ExternalID     string               `json:"external_id"`
+	ExternalName   string               `json:"external_name"`
+	SubjectType    identity.SubjectType `json:"subject_type,omitempty"`
+	SubjectID      int64                `json:"subject_id,omitempty"`
 }

internal/pkg/openidentity/openidentity_test.go

@@ -0,0 +1,30 @@
+package openidentity
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+func TestExternalUserJSONUsesSnakeCaseFields(t *testing.T) {
+	payload, err := json.Marshal(ExternalUser{
+		ExternalID:   "user:1",
+		ExternalName: "test",
+		SubjectID:    1,
+	})
+	if err != nil {
+		t.Fatalf("marshal external user: %v", err)
+	}
+
+	text := string(payload)
+	for _, field := range []string{`"external_id"`, `"external_name"`, `"subject_id"`} {
+		if !strings.Contains(text, field) {
+			t.Fatalf("expected %s in %s", field, text)
+		}
+	}
+	for _, field := range []string{"externalId", "externalName", "subjectId"} {
+		if strings.Contains(text, field) {
+			t.Fatalf("unexpected camelCase field %q in %s", field, text)
+		}
+	}
+}