Add initial frontend quality gates and TS hardening (#418)

Co-authored-by: Erion De Andrade <[email protected]>

app/src/App.tsx

@@ -121,7 +121,6 @@ function App() {
       console.log('Dev mode: Skipping auto-start of server (run it separately)');
       setServerReady(true); // Mark as ready so UI doesn't show loading screen
       // Mark that server was not started by app (so we don't try to stop it on close)
-      // @ts-expect-error - adding property to window
       window.__voiceboxServerStartedByApp = false;
       return;
     }
@@ -144,13 +143,11 @@ function App() {
         useServerStore.getState().setServerUrl(serverUrl);
         setServerReady(true);
         // Mark that we started the server (so we know to stop it on close)
-        // @ts-expect-error - adding property to window
         window.__voiceboxServerStartedByApp = true;
       })
       .catch((error) => {
         console.error('Failed to auto-start server:', error);
         serverStartingRef.current = false;
-        // @ts-expect-error - adding property to window
         window.__voiceboxServerStartedByApp = false;
 
         // Only fall back to health-check polling when the error indicates the