fix: stop keyboard-loop on mobile camera failure + guard drawer behind login

- handleCameraError() now sets scanningActive=false and resets codeReader
  so ZXing can't fire more callbacks that re-create the manual input and
  re-focus it — mobile keyboard was popping repeatedly
- openDrawer() now checked loginOverlay.hidden before opening, so drawer
  can't appear behind the login screen

static/index.html

@@ -2477,6 +2477,8 @@
     // DRAWER
     // =========================================================================
     function openDrawer() {
+      // Don't open drawer when login overlay is showing
+      if (!document.getElementById('loginOverlay').classList.contains('hidden')) return;
       document.getElementById('drawer').classList.add('open');
       document.getElementById('drawerOverlay').classList.add('open');
       // Highlight current tab in drawer
@@ -2929,6 +2931,14 @@
     }
 
     function handleCameraError(e) {
+      // Stop scanning so ZXing doesn't fire more callbacks that re-create the
+      // fallback UI in a loop — each re-create re-focuses the input, causing
+      // the mobile keyboard to pop repeatedly.
+      scanningActive = false;
+      if (codeReader) {
+        try { codeReader.reset(); } catch (_) { /* ignore */ }
+        codeReader = null;
+      }
       setScanStatus('Camera failed: ' + e.message, 'error');
       const ph = document.getElementById('cameraPlaceholder');
       if (ph) {