test: minimal vitest harness for backend and frontend

Ported from amal66/mike#24 onto current main; lockfiles regenerated against
this tree. Adds vitest as a dev dependency with a `test` script in both
packages, excludes test files from the backend tsc build, and seeds one
suite per package (backend: downloadTokens, 12 tests; frontend: cn() utils,
8 tests). Verified locally: backend 12/12, frontend 8/8 passing.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/package.json

@@ -7,6 +7,7 @@
         "build": "next build",
         "start": "next start",
         "lint": "eslint",
+        "test": "vitest run",
         "preview": "opennextjs-cloudflare build && opennextjs-cloudflare preview",
         "deploy": "opennextjs-cloudflare build && opennextjs-cloudflare deploy",
         "upload": "opennextjs-cloudflare build && opennextjs-cloudflare upload",
@@ -73,6 +74,7 @@
         "tailwindcss": "^4",
         "tw-animate-css": "^1.4.0",
         "typescript": "^5",
+        "vitest": "^4.1.9",
         "wrangler": "^4.90.0"
     },
     "license": "AGPL-3.0-only"

frontend/src/app/lib/utils.test.ts

@@ -0,0 +1,45 @@
+import { describe, expect, it } from "vitest";
+import { cn, diceCoefficient, isFuzzyMatch } from "./utils";
+
+describe("cn", () => {
+    it("joins truthy class names and drops falsy ones", () => {
+        expect(cn("a", false && "b", undefined, "c")).toBe("a c");
+    });
+
+    it("merges conflicting tailwind classes, keeping the last", () => {
+        expect(cn("px-2", "px-4")).toBe("px-4");
+    });
+});
+
+describe("diceCoefficient", () => {
+    it("returns 1 for identical strings (ignoring case and punctuation)", () => {
+        expect(diceCoefficient("Hello, World!", "hello world")).toBe(1);
+    });
+
+    it("returns 0 when either input is empty", () => {
+        expect(diceCoefficient("", "anything")).toBe(0);
+        expect(diceCoefficient("anything", "")).toBe(0);
+    });
+
+    it("returns a partial score for partially overlapping strings", () => {
+        const score = diceCoefficient("night", "nacht");
+        expect(score).toBeGreaterThan(0);
+        expect(score).toBeLessThan(1);
+    });
+});
+
+describe("isFuzzyMatch", () => {
+    it("matches near-identical strings above the default threshold", () => {
+        expect(isFuzzyMatch("organization", "organisation")).toBe(true);
+    });
+
+    it("rejects clearly different strings", () => {
+        expect(isFuzzyMatch("apple", "zebra")).toBe(false);
+    });
+
+    it("respects a custom threshold", () => {
+        // "night" vs "nacht" scores ~0.25 — passes a low bar, fails a high one.
+        expect(isFuzzyMatch("night", "nacht", 0.1)).toBe(true);
+        expect(isFuzzyMatch("night", "nacht", 0.9)).toBe(false);
+    });
+});