fix: Vite type declaration, non-idempotent retry, hardcoded test IP

- Add frontend/src/vite-env.d.ts (reference vite/client) to fix vue-tsc build
- Restrict axios-retry to GET/HEAD/OPTIONS only (avoid replaying mutations)
- Convert test_upstream.py to accept URL via CLI args instead of hardcoded IP

frontend/src/api/index.ts

@@ -11,14 +11,17 @@ export const api = axios.create({
 axiosRetry(api, {
   retries: 3,
   retryDelay: axiosRetry.exponentialDelay,
+  onRetry: (_retryCount, _err, _requestConfig) => {
+    // no-op — could log in dev
+  },
+  // Only retry idempotent methods — never retry POST/PUT/PATCH/DELETE
   retryCondition: (err) => {
+    const method = (err.config?.method ?? '').toUpperCase()
+    if (!['GET', 'HEAD', 'OPTIONS'].includes(method)) return false
     // Retry on network errors or 5xx, but never on 401/403/404/4xx
     if (!err.response) return true
     return err.response.status >= 500 && err.response.status < 600
   },
-  onRetry: (_retryCount, _err, _requestConfig) => {
-    // no-op — could log in dev
-  },
 })
 
 api.interceptors.response.use(