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。

contract/customer_access.go

@@ -0,0 +1,53 @@
+package contract
+
+import (
+	"context"
+	"strings"
+	"time"
+)
+
+// CustomerAccessProof is a host-verified, short-lived customer request proof.
+// It intentionally contains no password, bearer token, card number, or device
+// number. The opaque SessionID can only be issued and validated by the host.
+type CustomerAccessProof struct {
+	SessionID      string
+	TargetType     string
+	TargetID       int64
+	ConversationID int64
+	MessageID      int64
+	RequestID      string
+	ExpiresAt      time.Time
+}
+
+type customerAccessProofContextKey struct{}
+
+// WithCustomerAccessProof attaches a copy of a host-verified proof to the
+// current request. Agent Desk propagates only these claims into async runs.
+func WithCustomerAccessProof(ctx context.Context, proof CustomerAccessProof) context.Context {
+	return context.WithValue(ctx, customerAccessProofContextKey{}, proof)
+}
+
+// CustomerAccessProofFromContext returns only a structurally valid, live
+// proof. The host must still verify SessionID against its server-side store.
+func CustomerAccessProofFromContext(ctx context.Context) (CustomerAccessProof, bool) {
+	proof, ok := ctx.Value(customerAccessProofContextKey{}).(CustomerAccessProof)
+	if !ok || strings.TrimSpace(proof.SessionID) == "" || proof.TargetID <= 0 ||
+		(strings.TrimSpace(proof.TargetType) != "card" && strings.TrimSpace(proof.TargetType) != "device") ||
+		proof.ExpiresAt.IsZero() || !proof.ExpiresAt.After(time.Now()) {
+		return CustomerAccessProof{}, false
+	}
+	return proof, true
+}
+
+// BindCustomerAccessProofToMessage binds the current request proof to the
+// exact persisted customer message that triggered an async Agent run.
+func BindCustomerAccessProofToMessage(ctx context.Context, conversationID, messageID int64, requestID string) context.Context {
+	proof, ok := CustomerAccessProofFromContext(ctx)
+	if !ok {
+		return ctx
+	}
+	proof.ConversationID = conversationID
+	proof.MessageID = messageID
+	proof.RequestID = strings.TrimSpace(requestID)
+	return WithCustomerAccessProof(ctx, proof)
+}