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/client-translation-files.test.ts

@@ -0,0 +1,38 @@
+import { describe, expect, it } from "vitest";
+import {
+	CLIENT_TRANSLATION_FILES,
+	getClientTranslationFile,
+} from "./client-translation-files";
+
+describe("getClientTranslationFile", () => {
+	it("returns the file for a known id", () => {
+		const file = getClientTranslationFile("ui-texts-it");
+		expect(file?.relPath).toBe("public/nitro-assets/config/UITexts.json5");
+		expect(file?.format).toBe("json5");
+	});
+
+	it("returns undefined for unknown ids", () => {
+		expect(getClientTranslationFile("../../etc/passwd")).toBeUndefined();
+		expect(getClientTranslationFile("nope")).toBeUndefined();
+	});
+});
+
+describe("CLIENT_TRANSLATION_FILES", () => {
+	it("has unique ids (doubles as the path-traversal whitelist)", () => {
+		const ids = CLIENT_TRANSLATION_FILES.map((f) => f.id);
+		expect(new Set(ids).size).toBe(ids.length);
+	});
+
+	it("every relPath is inside the allowed public tree", () => {
+		for (const f of CLIENT_TRANSLATION_FILES) {
+			expect(f.relPath).toMatch(/^public\//);
+			expect(f.relPath).not.toContain("..");
+		}
+	});
+
+	it("formats are either json5 or json", () => {
+		for (const f of CLIENT_TRANSLATION_FILES) {
+			expect(["json5", "json"]).toContain(f.format);
+		}
+	});
+});