chore: clear the mechanical lint and type findings

Dead imports and locals removed, each blocks keyed, `any` narrowed to unknown.
Two context setters kept their calls and lost only the unused binding; the
settings redirect no longer awaits a parent whose data it discards. A leading
underscore now marks a binding that only holds a position.

frontend/src/routes/api/[...path]/+server.ts

@@ -137,7 +137,7 @@ export const DELETE: RequestHandler = async ({ params, locals, fetch, request, u
 		const headers = prepareRequest(locals, request);
 
 		// DELETE may or may not have a body
-		let options: RequestInit = {
+		const options: RequestInit = {
 			method: 'DELETE',
 			headers
 		};