a11y: focus-visible and skip link for forms/nav

See PR body.

Author: tapheret2

src/App.tsx

@@ -6,6 +6,9 @@ import RequestPage from "./pages/Request";
 
 export default function App() {
   return (
+    <>
+      <a className="skip-link" href="#main">Skip to content</a>
+
     <div className="min-h-screen bg-rock-900 text-white">
       <Navbar />
       <main className="max-w-5xl mx-auto p-6">

src/styles/a11y.css

@@ -0,0 +1,29 @@
+/* Accessibility pass: forms + navigation (GFI) */
+:focus-visible {
+  outline: 2px solid #2563eb;
+  outline-offset: 2px;
+}
+.skip-link {
+  position: absolute;
+  left: -999px;
+  top: 0;
+  background: #fff;
+  color: #000;
+  padding: 8px;
+  z-index: 1000;
+}
+.skip-link:focus {
+  left: 8px;
+}
+nav a:focus-visible,
+button:focus-visible,
+input:focus-visible,
+select:focus-visible,
+textarea:focus-visible {
+  outline: 2px solid #2563eb;
+  outline-offset: 2px;
+}
+label {
+  display: inline-block;
+  margin-bottom: 0.25rem;
+}