fix(frontend): correct path length check for workspace download requests

The isWorkspaceDownloadRequest function was checking for path.length >= 4,
but the pattern api/workspace/files/{id}/download has 5 segments. This
allowed malformed requests missing the file_id to be incorrectly routed
through the binary download handler.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

autogpt_platform/frontend/src/app/api/proxy/[...path]/route.ts

@@ -20,9 +20,9 @@ function buildBackendUrl(path: string[], queryString: string): string {
  * Check if this is a workspace file download request that needs binary response handling.
  */
 function isWorkspaceDownloadRequest(path: string[]): boolean {
-  // Match pattern: api/workspace/files/{id}/download
+  // Match pattern: api/workspace/files/{id}/download (5 segments)
   return (
-    path.length >= 4 &&
+    path.length >= 5 &&
     path[0] === "api" &&
     path[1] === "workspace" &&
     path[2] === "files" &&