Fix: trim prefix slash in ListObjectVersionsHandler (#7919)

* Fix: trim prefix slash in ListObjectVersionsHandler

* Add test for ListObjectVersions prefix handling

Test validates that prefix normalization works correctly with and without
leading slashes, ensuring the fix for /Veeam/Archive/ style prefixes.

* Simplify prefix test to validate normalization logic

The test now validates that the prefix normalization (TrimPrefix) works
correctly and that normalized prefixes match paths as expected. This is
a focused unit test that validates the core fix without requiring complex
mocking of the filer client.

* Enhance prefix test with full matchesPrefixFilter logic

Added test cases for directory traversal including:
- Directory matching with trailing slash
- canDescend logic for recursive directory search
- Full simulation of matchesPrefixFilter behavior

This provides more comprehensive coverage of the prefix normalization
fix and ensures it works correctly for both files and directories.

weed/s3api/s3api_object_versioning.go

@@ -985,7 +985,7 @@ func (s3a *S3ApiServer) ListObjectVersionsHandler(w http.ResponseWriter, r *http
 	// Parse query parameters
 	query := r.URL.Query()
 	originalPrefix := query.Get("prefix") // Keep original prefix for response
-	prefix := originalPrefix              // Use for internal processing
+	prefix := strings.TrimPrefix(originalPrefix, "/")
 	// Note: prefix is used for filtering relative to bucket root, so no leading slash needed
 
 	keyMarker := query.Get("key-marker")