test: add unit tests for pure logic modules

Add 22 test files covering imager, soundtracks, browser-headers, source-keys (figure/pet/effect), effect-source, plus catalog-translations, catalog-layouts, client-translation-files, translations-utils, and various admin/services/helpers modules. Total test count increases by 120+.

src/lib/catalog-layouts.test.ts

@@ -0,0 +1,28 @@
+import { describe, expect, it } from "vitest";
+import { CATALOG_LAYOUTS, LAYOUT_DESCRIPTIONS } from "./catalog-layouts";
+
+describe("CATALOG_LAYOUTS", () => {
+	it("contains the common Habbo layouts", () => {
+		for (const layout of [
+			"frontpage",
+			"default_3x3",
+			"spaces_new",
+			"marketplace",
+			"room_bundle",
+		]) {
+			expect(CATALOG_LAYOUTS).toContain(layout);
+		}
+	});
+
+	it("has a description for every layout", () => {
+		for (const layout of CATALOG_LAYOUTS) {
+			expect(LAYOUT_DESCRIPTIONS[layout]).toBeTruthy();
+		}
+	});
+
+	it("descriptions are non-empty", () => {
+		for (const desc of Object.values(LAYOUT_DESCRIPTIONS)) {
+			expect(desc.length).toBeGreaterThan(0);
+		}
+	});
+});