fix(go): Add tenant filter to file queries (#16526)

## Summary

- Add `tenant_id` filtering to `FileDAO.Query`.
- Pass tenant IDs through existing file query call sites.
- Prevent cross-tenant filename and folder duplicate checks.

internal/handler/file_commit.go

@@ -97,7 +97,7 @@ func (h *FileCommitHandler) resolveDatasetFolderID(datasetID string) (string, er
 	if err != nil {
 		return "", err
 	}
-	files := h.fileDAO.Query(kb.Name, "")
+	files := h.fileDAO.Query(kb.Name, "", kb.TenantID)
 	for _, f := range files {
 		if f.SourceType == string(entity.FileSourceKnowledgebase) && f.Type == "folder" && f.TenantID == kb.TenantID {
 			return f.ID, nil