Fix native white screen: relative asset base + boot crash guard

Two changes targeting the post-update white screen on the Zapstore APK:

1. vite.config: set base './' when CAPACITOR_BUILD is set. In a native
   WebView the bundle is served from the local filesystem, so absolute '/'
   asset paths are the classic cause of a silent white screen. The web
   deploy keeps '/'. This is the documented Capacitor requirement and is
   zero-risk to the working web build.

2. index.html: add a dependency-free "boot crash guard" that runs before
   the app bundle and paints any uncaught error / unhandled rejection —
   plus a 12s "did not render" timeout — directly to the screen using
   inline styles only. A boot failure that would otherwise be an
   info-less white screen now shows the actual error ON DEVICE, with no
   USB/remote-debugging needed. main.tsx signals a clean boot to cancel
   the timeout guard.

Co-authored-by: shakespeare.diy <assistant@shakespeare.diy>

index.html

@@ -46,6 +46,58 @@
   </head>
   <body>
     <div id="root"></div>
+
+    <!--
+      BOOT CRASH GUARD (native-safe).
+      Runs before the app bundle and paints any uncaught boot error directly to
+      the screen using inline styles only — so a failure that would otherwise be
+      a silent white screen (bundle load error, module-level throw, missing CSS)
+      becomes a readable message on device, with no cable/remote-debug needed.
+      If the app boots normally it clears itself and costs nothing.
+    -->
+    <script>
+      (function () {
+        var shown = false;
+        function paint(kind, err) {
+          if (shown) return;
+          shown = true;
+          try {
+            var msg = (err && (err.stack || err.message)) ? (err.stack || err.message) : String(err);
+            var el = document.createElement('div');
+            el.setAttribute('style', [
+              'position:fixed', 'inset:0', 'z-index:2147483647',
+              'background:#000', 'color:#fff', 'padding:20px',
+              'font:13px/1.5 -apple-system,system-ui,monospace',
+              'overflow:auto', '-webkit-overflow-scrolling:touch'
+            ].join(';'));
+            el.innerHTML =
+              '<div style="color:#ff0040;font-weight:700;font-size:16px;margin-bottom:8px">SkateSpots failed to start</div>' +
+              '<div style="color:#9ca3af;margin-bottom:12px">' + kind + '</div>' +
+              '<pre style="white-space:pre-wrap;word-break:break-word;color:#f3f4f6;margin:0">' +
+              (msg ? msg.replace(/[<>&]/g, function (c) { return { '<': '&lt;', '>': '&gt;', '&': '&amp;' }[c]; }) : '(no message)') +
+              '</pre>' +
+              '<button onclick="location.reload()" style="margin-top:16px;padding:10px 16px;background:#ff0040;color:#000;border:0;border-radius:8px;font-weight:700">Reload</button>';
+            document.body.appendChild(el);
+          } catch (e) { /* last resort: nothing we can do */ }
+        }
+        window.addEventListener('error', function (e) {
+          paint('Uncaught error', e.error || e.message);
+        });
+        window.addEventListener('unhandledrejection', function (e) {
+          paint('Unhandled promise rejection', e.reason);
+        });
+        // If nothing has rendered into #root after 12s, surface a hint.
+        setTimeout(function () {
+          var root = document.getElementById('root');
+          if (root && root.childElementCount === 0) {
+            paint('App did not render (timeout)', 'The bundle loaded but nothing mounted within 12s. This usually means a boot-time exception was swallowed.');
+          }
+        }, 12000);
+        // Let the app signal a clean boot to cancel the timeout guard.
+        window.__SKATESPOTS_BOOTED__ = function () { shown = true; };
+      })();
+    </script>
+
     <script type="module" src="/src/main.tsx"></script>
   </body>
 </html>

src/main.tsx

@@ -81,3 +81,11 @@ createRoot(document.getElementById("root")!).render(
     <App />
   </ErrorBoundary>
 );
+
+// Tell the boot crash guard (in index.html) that the app mounted successfully,
+// so its "did not render" timeout doesn't fire.
+try {
+  (window as unknown as { __SKATESPOTS_BOOTED__?: () => void }).__SKATESPOTS_BOOTED__?.();
+} catch {
+  /* no-op */
+}

vite.config.ts

@@ -5,6 +5,11 @@ import { defineConfig } from "vitest/config";
 
 // https://vitejs.dev/config/
 export default defineConfig(() => ({
+  // In a native Capacitor WebView the bundle is served from the local
+  // filesystem, so assets must be referenced with RELATIVE paths ('./…').
+  // Absolute '/…' paths are the classic cause of a white screen on device.
+  // The regular web deploy keeps '/' (served from a domain root).
+  base: process.env.CAPACITOR_BUILD ? './' : '/',
   server: {
     host: "::",
     port: 8080,