Use native FormData in controller route tests

Node's FormData and Blob do what the form-data package did here, and
fetch sets the multipart Content-Type header itself.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

package.json

@@ -46,7 +46,6 @@
 		"@types/node": "catalog:",
 		"c8": "^12.0.0",
 		"express": "catalog:",
-		"form-data": "^4.0.6",
 		"jsonwebtoken": "catalog:",
 		"mocha": "^11.8.0",
 		"oxlint": "^1.88.0",