feat: add keyboard navigation, escape-to-close modals, skip-to-content (A11Y-02)

All modals now close with Escape key. Interactive card divs respond to
Enter key. Skip-to-content link added to Dashboard layout. All Web5 and
Settings modals get role=dialog, aria-modal, and escape handlers.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

neode-ui/src/style.css

@@ -17,6 +17,35 @@
   font-style: normal;
 }
 
+/* Skip to main content — keyboard navigation accessibility */
+.skip-to-content {
+  position: absolute;
+  left: -9999px;
+  top: auto;
+  width: 1px;
+  height: 1px;
+  overflow: hidden;
+  z-index: 9999;
+}
+.skip-to-content:focus {
+  position: fixed;
+  top: 12px;
+  left: 50%;
+  transform: translateX(-50%);
+  width: auto;
+  height: auto;
+  overflow: visible;
+  padding: 8px 24px;
+  background: rgba(0, 0, 0, 0.85);
+  color: white;
+  border: 1px solid rgba(255, 255, 255, 0.3);
+  border-radius: 8px;
+  font-size: 14px;
+  font-weight: 500;
+  text-decoration: none;
+  backdrop-filter: blur(12px);
+}
+
 /* Controller / keyboard navigation - soft glow only (no box outline) */
 *:focus-visible {
   outline: none;