feat: implement esting suite using Vitest and add to ci

frontend/vitest.config.ts

@@ -0,0 +1,23 @@
+import tailwindcss from "@tailwindcss/vite";
+import react from "@vitejs/plugin-react";
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  envDir: "..",
+  plugins: [react(), tailwindcss()],
+  test: {
+    env: {
+      VITE_API_URL: "http://piku-server",
+    },
+    environment: "jsdom",
+    globals: true,
+    setupFiles: ["./test/setup.ts"],
+    coverage: {
+      provider: "v8",
+      reporter: ["text", "html"],
+      include: ["**/*.ts", "**/*.tsx"],
+      exclude: ["node_modules", "dist", "**/*.d.ts", "./test/**"],
+      thresholds: { lines: 80, functions: 80, branches: 80 },
+    },
+  },
+});