feat: add community enhancements — password reset, audit logs, multi-source backup

Three community-requested features:

1. CLI password reset: `backupx reset-password --username admin --password xxx`
   Docker users can run via `docker exec`. No full app init needed.

2. Audit logging: async fire-and-forget audit trail for all key operations
   (login, CRUD on tasks/targets/records, settings changes).
   New UI page at /audit with category filter and pagination.

3. Multi-source path backup: file backup tasks now support multiple source
   directories packed into a single tar archive. Backward compatible with
   existing single sourcePath field.

server/internal/service/backup_record_service.go

@@ -2,6 +2,7 @@ package service
 
 import (
 	"context"
+	"encoding/json"
 	"strings"
 	"time"
 
@@ -38,8 +39,9 @@ type BackupRecordSummary struct {
 
 type BackupRecordDetail struct {
 	BackupRecordSummary
-	LogContent string            `json:"logContent"`
-	LogEvents  []backup.LogEvent `json:"logEvents,omitempty"`
+	LogContent           string                    `json:"logContent"`
+	LogEvents            []backup.LogEvent         `json:"logEvents,omitempty"`
+	StorageUploadResults []StorageUploadResultItem  `json:"storageUploadResults,omitempty"`
 }
 
 type BackupRecordService struct {
@@ -130,5 +132,12 @@ func toBackupRecordDetail(item *model.BackupRecord, logHub *backup.LogHub) *Back
 			detail.LogContent = strings.Join(lines, "\n")
 		}
 	}
+	// 解析多目标上传结果
+	if strings.TrimSpace(item.StorageUploadResults) != "" {
+		var uploadResults []StorageUploadResultItem
+		if err := json.Unmarshal([]byte(item.StorageUploadResults), &uploadResults); err == nil {
+			detail.StorageUploadResults = uploadResults
+		}
+	}
 	return detail
 }