修复: 审计日志补充操作详情 + 版本号注入修复

1. 审计日志：所有 handler 的 recordAudit 调用补充有意义的 detail，
   包括创建/更新时记录类型、删除时记录 ID、设置变更时记录修改的 key
2. 版本号：Makefile 的 run/build 都通过 ldflags 注入 git 版本号，
   开发模式不再显示 "dev"

server/internal/http/settings_handler.go

@@ -1,6 +1,9 @@
 package http
 
 import (
+	"fmt"
+	"strings"
+
 	"backupx/server/internal/apperror"
 	"backupx/server/internal/service"
 	"backupx/server/pkg/response"
@@ -36,6 +39,10 @@ func (h *SettingsHandler) Update(c *gin.Context) {
 		response.Error(c, err)
 		return
 	}
-	recordAudit(c, h.auditService, "settings", "update", "settings", "", "", "")
+	keys := make([]string, 0, len(input))
+	for k := range input {
+		keys = append(keys, k)
+	}
+	recordAudit(c, h.auditService, "settings", "update", "settings", "", "", fmt.Sprintf("修改设置: %s", strings.Join(keys, ", ")))
 	response.Success(c, settings)
 }