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/translations-utils.test.ts

@@ -0,0 +1,45 @@
+import { describe, expect, it } from "vitest";
+import { flattenObject, unflattenObject } from "./translations-utils";
+
+describe("flattenObject", () => {
+	it("flattens nested objects into dotted keys", () => {
+		const flat = flattenObject({ a: { b: { c: "x" } }, d: "y" });
+		expect(flat).toEqual({ "a.b.c": "x", d: "y" });
+	});
+
+	it("stringifies non-object values", () => {
+		expect(flattenObject({ n: 5, b: true, nil: null })).toEqual({
+			n: "5",
+			b: "true",
+			nil: "",
+		});
+	});
+
+	it("keeps arrays as-is via String()", () => {
+		expect(flattenObject({ list: ["a", "b"] })).toEqual({ list: "a,b" });
+	});
+
+	it("honours an explicit prefix", () => {
+		expect(flattenObject({ a: 1 }, "root")).toEqual({ "root.a": "1" });
+	});
+});
+
+describe("unflattenObject", () => {
+	it("rebuilds nested objects from dotted keys", () => {
+		expect(unflattenObject({ "a.b.c": "x", d: "y" })).toEqual({
+			a: { b: { c: "x" } },
+			d: "y",
+		});
+	});
+
+	it("creates intermediate objects as needed", () => {
+		expect(unflattenObject({ "x.y": "1", "x.z": "2" })).toEqual({
+			x: { y: "1", z: "2" },
+		});
+	});
+
+	it("round-trips with flattenObject", () => {
+		const original = { menu: { home: "Home", items: { a: "A" } }, footer: "F" };
+		expect(unflattenObject(flattenObject(original))).toEqual(original);
+	});
+});