feat: add dayjs, axios, and environment variable configuration

- Add dayjs with duration plugin pre-configured
- Add axios instance with auth token injection and 401 redirect
- Add VITE_API_BASE_URL, VITE_APP_TITLE, and VITE_ENABLE_MOCK env declarations
- Add .env.example with documented variables

package.json

@@ -19,6 +19,8 @@
   },
   "dependencies": {
     "@tailwindcss/vite": "^4.3.1",
+    "axios": "^1.18.0",
+    "dayjs": "^1.11.21",
     "pinia": "^3.0.4",
     "tailwindcss": "^4.3.1",
     "vue": "^3.5.32",