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/business_action_tool.go

@@ -0,0 +1,87 @@
+package contract
+
+import (
+	"context"
+	"errors"
+)
+
+type BusinessActionFailureOutcome string
+
+const (
+	// BusinessActionFailureRetryable means execution failed before the host
+	// operation could have produced a side effect. The same idempotency key may
+	// be claimed again.
+	BusinessActionFailureRetryable BusinessActionFailureOutcome = "retryable_failed"
+	// BusinessActionFailureUnknown means the host may have committed the side
+	// effect even though Agent Desk did not receive a definitive response. Such
+	// an invocation must be reconciled instead of replayed automatically.
+	BusinessActionFailureUnknown BusinessActionFailureOutcome = "unknown_outcome"
+)
+
+// BusinessActionResult is the customer-safe result returned after a confirmed
+// host business operation. Message is sent to the customer verbatim; Data is
+// retained only for idempotent replay and future structured clients.
+type BusinessActionResult struct {
+	Message string `json:"message"`
+	Data    any    `json:"data,omitempty"`
+}
+
+// BusinessActionError separates a customer-safe explanation from its internal
+// cause so model observations and chat replies never expose infrastructure
+// errors returned by the host application.
+type BusinessActionError struct {
+	Message string
+	Cause   error
+	Outcome BusinessActionFailureOutcome
+}
+
+func (e *BusinessActionError) Error() string {
+	return e.Message
+}
+
+func (e *BusinessActionError) Unwrap() error {
+	return e.Cause
+}
+
+func NewBusinessActionError(message string, cause error) error {
+	return &BusinessActionError{Message: message, Cause: cause, Outcome: BusinessActionFailureUnknown}
+}
+
+func NewRetryableBusinessActionError(message string, cause error) error {
+	return &BusinessActionError{Message: message, Cause: cause, Outcome: BusinessActionFailureRetryable}
+}
+
+func NewUnknownOutcomeBusinessActionError(message string, cause error) error {
+	return &BusinessActionError{Message: message, Cause: cause, Outcome: BusinessActionFailureUnknown}
+}
+
+func BusinessActionErrorOutcome(err error) BusinessActionFailureOutcome {
+	var actionErr *BusinessActionError
+	if errors.As(err, &actionErr) {
+		return actionErr.Outcome
+	}
+	return ""
+}
+
+// BusinessActionTool lets the host expose a narrowly scoped write operation.
+// Preview must perform read-only validation and produce the exact confirmation
+// prompt. Execute must independently reload and validate all mutable business
+// state before committing the operation.
+type BusinessActionTool struct {
+	Code          string
+	Description   string
+	CustomerTypes []string
+	InputSchema   map[string]any
+	// MatchIntent lets the host identify an unambiguous customer command that
+	// must enter the confirmation flow without relying on the language model to
+	// select a tool. It must be side-effect free.
+	MatchIntent func(string) bool
+	Preview     func(context.Context, BusinessReadContext, map[string]any) (string, error)
+	// BindConfirmation binds the generated server checkpoint and canonical
+	// arguments to the verified request that prepared the action.
+	BindConfirmation func(context.Context, BusinessReadContext, map[string]any, string) error
+	// AuthorizeConfirmation re-verifies the current confirmation request and
+	// the previously bound checkpoint immediately before idempotency claiming.
+	AuthorizeConfirmation func(context.Context, BusinessReadContext, map[string]any, string) error
+	Execute               func(context.Context, BusinessReadContext, map[string]any) (*BusinessActionResult, error)
+}