fix: resolve request hanging and proxy IPv4/IPv6 mismatch

- Fix Vite dev proxy: change target from localhost to 127.0.0.1 to
  prevent IPv6/IPv4 mismatch (Vite binds IPv6, backend binds IPv4,
  localhost resolves to ::1 on macOS causing proxy timeout)
- Fix SingleRequest loading state: add setLoading(false) in pre-request
  script error path and a finally block so the spinner always clears
  even on failure

All tests pass: 539 backend + 356 frontend

Author: Scarage1

frontend/src/pages/SingleRequest.tsx

@@ -152,6 +152,7 @@ export default function SingleRequest() {
           scriptError: preResult.error,
         });
         toast.error('Pre-request script failed', preResult.error);
+        setLoading(tabId, false);
         return;
       }
 
@@ -268,6 +269,8 @@ export default function SingleRequest() {
         consoleLogs: preScriptLogs,
       });
       toast.error('Request failed', message);
+    } finally {
+      setLoading(tabId, false);
     }
   }, [tab, envVars, setLoading, setResponse, addToHistory]);
 

frontend/vite.config.ts

@@ -21,15 +21,15 @@ export default defineConfig({
     host: true,
     proxy: {
       '/api': {
-        target: 'http://localhost:8000',
+        target: 'http://127.0.0.1:8000',
         changeOrigin: true,
       },
       '/health': {
-        target: 'http://localhost:8000',
+        target: 'http://127.0.0.1:8000',
         changeOrigin: true,
       },
       '/ws': {
-        target: 'ws://localhost:8000',
+        target: 'ws://127.0.0.1:8000',
         ws: true,
       },
     },