chore: CSP script nonces, deploy health check, dead-code cleanup

Add per-request CSP nonces (drop script unsafe-inline), post-deploy /api/health gate, bump next-auth to beta.32, and remove unused motion/cache/permission helpers.

Co-authored-by: Cursor <[email protected]>

src/lib/redis-cache.ts

@@ -33,16 +33,6 @@ export async function redisCache<T>(
 	return fresh;
 }
 
-// TODO: Check of dit weg kan — niet geïmporteerd in de codebase
-export async function invalidateCache(key: string): Promise<void> {
-	if (!redis) return;
-	try {
-		await redis.del(key);
-	} catch {
-		// ignore
-	}
-}
-
 /**
  * Build a namespaced cache key for API routes.
  */