build(fc2c-i): add Vitest harness and run it in CI

frontend/package.json

@@ -10,6 +10,7 @@
     "dev": "vite",
     "build": "vite build",
     "preview": "vite preview",
+    "test:unit": "vitest run",
     "check": "vue-tsc --noEmit"
   },
   "dependencies": {
@@ -24,6 +25,7 @@
     "vite": "^5.2.0",
     "vue-tsc": "^2.0.0",
     "vite-plugin-vuetify": "^2.0.0",
-    "sass": "^1.71.0"
+    "sass": "^1.71.0",
+    "vitest": "^2.1.0"
   }
 }

frontend/vitest.config.js

@@ -0,0 +1,9 @@
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  test: {
+    environment: 'node',
+    include: ['test/**/*.spec.js'],
+    passWithNoTests: true
+  }
+})