fix: make useServerAction accept void-returning actions and remove dead queryCount

- Type run()'s action param as Promise<unknown> and cast result (Biome strips void from unions)
- Remove unused queryCount field increment in DbService (dead code)
- Reformat theme-contrast test pair assertions

src/lib/foundation/database.ts

@@ -19,7 +19,6 @@ export class DbService {
 	private readonly client: PrismaClient;
 	private lastHealthCheck = 0;
 	private healthCache: HealthStatus | null = null;
-	private queryCount = 0;
 	private readonly healthTtlMs = 10_000;
 
 	constructor() {
@@ -106,7 +105,6 @@ export class DbService {
 	}
 
 	async execute<T>(fn: (client: PrismaClient) => Promise<T>): Promise<T> {
-		this.queryCount++;
 		try {
 			return await fn(this.client);
 		} catch (cause) {