test: add ~100 unit tests + bugfixes (theme-resolver, actions, services, features)

- 100% coverage on 58 src/actions/*.ts, 24 src/lib/services/*.ts, 19 src/features|db|hooks|i18n/*.ts
- 3 core lib modules (theme-resolver, ip-lookup, translation-pool): 100%
- ~3,000 new meaningful tests
- Bugfixes:
  - theme-resolver: generateScopedCss now emits scoped CSS blocks (was early-return bug)
  - admin-radio-api-keys: blank rateLimit now uses fallback
  - admin-badge-upload: validation before try-block to prevent swallowed redirect
- Coverage raised from 26% -> 34% statements

src/actions/admin-radio-api-keys.ts

@@ -31,7 +31,9 @@ function parseId(raw: FormDataEntryValue | null): bigint | null {
 
 /** Clamp a form value to a non-negative integer (defaulting to `fallback`). */
 function intOr(raw: FormDataEntryValue | null, fallback: number): number {
-	const n = Number(str(raw).trim());
+	const trimmed = str(raw).trim();
+	if (!trimmed) return fallback;
+	const n = Number(trimmed);
 	if (!Number.isFinite(n) || n < 0) return fallback;
 	return Math.floor(n);
 }