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/hooks/use-server-action.ts

@@ -36,10 +36,7 @@ export function useServerAction(options: UseServerActionOptions = {}) {
 	const [isPending, startTransition] = useTransition();
 	const router = useRouter();
 
-	function run(
-		action: () => Promise<ActionResult | undefined | void>,
-		opts: RunOptions = {},
-	) {
+	function run(action: () => Promise<unknown>, opts: RunOptions = {}) {
 		const {
 			successMessage = "Saved successfully.",
 			errorMessage = "An error occurred.",
@@ -49,7 +46,7 @@ export function useServerAction(options: UseServerActionOptions = {}) {
 
 		startTransition(async () => {
 			try {
-				const result = await action();
+				const result = (await action()) as ActionResult | undefined;
 
 				if (!result || result.ok) {
 					toast.success(successMessage);