feat: auto-generate full package when uploading patch

- Add FullPackagePath, FullPackageSize, FullPackageHash to Version model
- When uploading patch, merge with base full package to create new full package
- Check update API returns full package info for download
- Add package_util.go with merge functions

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/internal/router/app/info.go

@@ -216,8 +216,18 @@ func handleAppCheckUpdate(c *gin.Context) {
 		}
 	}
 
-	// 确定下载地址：优先使用自定义地址
+	// 确定下载地址：优先使用完整包地址，其次自定义地址
 	downloadURL := latestVersion.FilePath
+	downloadSize := latestVersion.FileSize
+	downloadHash := latestVersion.FileHash
+
+	// 使用完整包地址（如果有）
+	if latestVersion.FullPackagePath != "" {
+		downloadURL = latestVersion.FullPackagePath
+		downloadSize = latestVersion.FullPackageSize
+		downloadHash = latestVersion.FullPackageHash
+	}
+	// 自定义地址优先级最高
 	if latestVersion.CustomDownloadURL != "" {
 		downloadURL = latestVersion.CustomDownloadURL
 	}
@@ -228,8 +238,8 @@ func handleAppCheckUpdate(c *gin.Context) {
 		"current_version": clientVersion,
 		"latest_version":  latestVersion.Version,
 		"download_url":    downloadURL,
-		"file_size":       latestVersion.FileSize,
-		"file_hash":       latestVersion.FileHash,
+		"file_size":       downloadSize,
+		"file_hash":       downloadHash,
 		"entry_file":      latestVersion.EntryFile,
 		"update_notes":    latestVersion.Description,
 		"update_strategy": updateStrategy,