Set up S3 testing infrastructure for backup implementation

- Add gofakes3 for in-process S3-compatible test server
- Create test server that runs on localhost:9999 with temp directory
- Implement basic S3 client wrapper with standard operations
- Add comprehensive tests for blob and metadata storage patterns
- Test cleanup properly removes temporary directories
- Use AWS SDK v2 for S3 operations with proper error handling

internal/cli/snapshot.go

@@ -37,7 +37,7 @@ func snapshotListCmd() *cobra.Command {
 	cmd.Flags().StringVar(&bucket, "bucket", "", "S3 bucket name")
 	cmd.Flags().StringVar(&prefix, "prefix", "", "S3 prefix")
 	cmd.Flags().IntVar(&limit, "limit", 10, "Maximum number of snapshots to list")
-	cmd.MarkFlagRequired("bucket")
+	_ = cmd.MarkFlagRequired("bucket")
 
 	return cmd
 }
@@ -61,8 +61,8 @@ func snapshotRmCmd() *cobra.Command {
 	cmd.Flags().StringVar(&bucket, "bucket", "", "S3 bucket name")
 	cmd.Flags().StringVar(&prefix, "prefix", "", "S3 prefix")
 	cmd.Flags().StringVar(&snapshot, "snapshot", "", "Snapshot ID to remove")
-	cmd.MarkFlagRequired("bucket")
-	cmd.MarkFlagRequired("snapshot")
+	_ = cmd.MarkFlagRequired("bucket")
+	_ = cmd.MarkFlagRequired("snapshot")
 
 	return cmd
 }
@@ -84,7 +84,7 @@ func snapshotLatestCmd() *cobra.Command {
 
 	cmd.Flags().StringVar(&bucket, "bucket", "", "S3 bucket name")
 	cmd.Flags().StringVar(&prefix, "prefix", "", "S3 prefix")
-	cmd.MarkFlagRequired("bucket")
+	_ = cmd.MarkFlagRequired("bucket")
 
 	return cmd
 }