Show fatal error overlay on startup

src/main.jsx

@@ -21,6 +21,37 @@ import { AuthProvider } from "./auth/AuthContext.jsx";
 // Import pour PWA install
 import { promptInstall } from './pwaInstall';
 
+function installGlobalErrorOverlay() {
+  if (typeof window === "undefined") return;
+  const show = (msg) => {
+    try {
+      let el = document.getElementById("sw-fatal");
+      if (!el) {
+        el = document.createElement("div");
+        el.id = "sw-fatal";
+        el.style.position = "fixed";
+        el.style.inset = "0";
+        el.style.background = "#0b0f1a";
+        el.style.color = "#e2e8f0";
+        el.style.zIndex = "999999";
+        el.style.padding = "24px";
+        el.style.fontFamily = "ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace";
+        el.style.whiteSpace = "pre-wrap";
+        document.body.appendChild(el);
+      }
+      el.textContent = `SocioWire error:\\n${msg}`;
+    } catch {}
+  };
+  window.addEventListener("error", (e) => {
+    show(e?.message || String(e));
+  });
+  window.addEventListener("unhandledrejection", (e) => {
+    show(e?.reason?.message || String(e?.reason || e));
+  });
+}
+
+installGlobalErrorOverlay();
+
 ReactDOM.createRoot(document.getElementById("root")).render(
   <React.StrictMode>
     <AuthProvider>