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/services/business_action_failure.go

@@ -0,0 +1,50 @@
+package services
+
+import (
+	"context"
+	"errors"
+	"io"
+	"net"
+	"net/url"
+	"strings"
+	"syscall"
+
+	"code.tczkiot.com/wlw/ai-agent/contract"
+)
+
+// businessActionFailureIsRetryable is deliberately conservative. Transport
+// failures can happen after the host has committed a write, so they always
+// produce unknown_outcome even when wrapped in a customer-safe error.
+func businessActionFailureIsRetryable(ctx context.Context, err error) bool {
+	if err == nil {
+		return true
+	}
+	if ctx != nil && ctx.Err() != nil {
+		return false
+	}
+	if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) ||
+		errors.Is(err, io.EOF) || errors.Is(err, io.ErrUnexpectedEOF) ||
+		errors.Is(err, syscall.ECONNRESET) || errors.Is(err, syscall.ECONNABORTED) ||
+		errors.Is(err, syscall.EPIPE) {
+		return false
+	}
+	var netErr net.Error
+	if errors.As(err, &netErr) && (netErr.Timeout() || netErr.Temporary()) {
+		return false
+	}
+	var urlErr *url.Error
+	if errors.As(err, &urlErr) {
+		return false
+	}
+	message := strings.ToLower(err.Error())
+	for _, marker := range []string{
+		"timeout", "timed out", "deadline exceeded", "context canceled",
+		"connection reset", "connection aborted", "broken pipe", "unexpected eof",
+		"server closed idle connection", "transport connection broken",
+	} {
+		if strings.Contains(message, marker) {
+			return false
+		}
+	}
+	return contract.BusinessActionErrorOutcome(err) == contract.BusinessActionFailureRetryable
+}