fix(security): undefined variable next referenced in route erro

The GET /schema route handler's function signature is `(req, res)` (only two parameters), but the catch block calls `next(err)`. Since `next` is not defined in this scope, this will throw a `ReferenceError` at runtime when an error occurs, potentially crashing the process or causing an unhandled rejection instead of properly returning an error response.

Affected files: schema.js

Signed-off-by: Trần Bách <45133811+barttran2k@users.noreply.github.com>

backend/routes/schema.js

@@ -18,7 +18,7 @@ router
 	/**
 	 * GET /schema
 	 */
-	.get(async (req, res) => {
+	.get(async (req, res, next) => {
 		try {
 			const swaggerJSON = await getCompiledSchema();