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/builders/notification_builder.go

@@ -10,7 +10,6 @@ import (
 )
 
 var (
-	ticketAssignedNotificationPattern       = regexp.MustCompile(`^工单 (.+) 已指派给你$`)
 	conversationAssignedNotificationPattern = regexp.MustCompile(`^会话 #([0-9]+) 已分配给你$`)
 )
 
@@ -58,8 +57,6 @@ func localizeNotificationText(item *models.Notification, locale string) (string,
 		return title, content
 	}
 	switch strings.TrimSpace(item.NotificationType) {
-	case "ticket_assigned":
-		return localizeTicketAssignedNotification(title, content)
 	case "conversation_assigned":
 		return localizeConversationAssignedNotification(title, content)
 	default:
@@ -67,22 +64,6 @@ func localizeNotificationText(item *models.Notification, locale string) (string,
 	}
 }
 
-func localizeTicketAssignedNotification(title string, content string) (string, string) {
-	lines := splitNotificationLines(content)
-	if len(lines) == 0 {
-		return localizeNotificationTitle(title), content
-	}
-	if matches := ticketAssignedNotificationPattern.FindStringSubmatch(lines[0]); len(matches) == 2 {
-		lines[0] = i18nx.Getf(i18nx.LocaleEnUS, "notification.ticketAssigned.line", matches[1])
-	}
-	for i, line := range lines[1:] {
-		if reason, ok := strings.CutPrefix(line, "指派原因: "); ok {
-			lines[i+1] = i18nx.Getf(i18nx.LocaleEnUS, "notification.ticketAssigned.reason", reason)
-		}
-	}
-	return localizeNotificationTitle(title), strings.Join(lines, "\n")
-}
-
 func localizeConversationAssignedNotification(title string, content string) (string, string) {
 	lines := splitNotificationLines(content)
 	if len(lines) == 0 {
@@ -105,8 +86,6 @@ func localizeConversationAssignedNotification(title string, content string) (str
 
 func localizeNotificationTitle(title string) string {
 	switch strings.TrimSpace(title) {
-	case "工单指派提醒":
-		return i18nx.Getf(i18nx.LocaleEnUS, "notification.ticketAssigned.title")
 	case "会话转接提醒":
 		return i18nx.Getf(i18nx.LocaleEnUS, "notification.conversationTransferred.title")
 	case "会话自动分配提醒":