feat: add reading list page and link it from site navigation

New reading.html renders the data file into a #reading-list container and
marks itself as the current page. Home and contact pages gain a Reading nav
link. CSS adds responsive category/list styles (two columns on wide
screens) so long lists stay scannable.

css/style.css

@@ -120,6 +120,59 @@ button[type="submit"]:hover {
   filter: brightness(1.1);
 }
 
+/* --- Reading list --- */
+.reading-category {
+  margin-bottom: 2rem;
+}
+
+.reading-category h2 {
+  font-size: 1.1rem;
+  border-bottom: 1px solid var(--border);
+  padding-bottom: 0.35rem;
+  margin-bottom: 0.75rem;
+}
+
+.reading-list {
+  margin: 0;
+  padding: 0;
+  list-style: none;
+  display: grid;
+  gap: 0.75rem;
+}
+
+.reading-entry {
+  display: grid;
+  gap: 0.1rem;
+}
+
+.reading-link {
+  color: var(--accent);
+  text-decoration: none;
+  overflow-wrap: anywhere;
+}
+
+.reading-link:hover,
+.reading-link:focus {
+  text-decoration: underline;
+}
+
+.reading-note {
+  margin: 0;
+  color: var(--muted);
+  font-size: 0.9rem;
+}
+
+.reading-empty {
+  color: var(--muted);
+}
+
+/* Two columns once there is room — keeps long lists scannable. */
+@media (min-width: 40rem) {
+  .reading-list {
+    grid-template-columns: repeat(2, minmax(0, 1fr));
+  }
+}
+
 /* --- Footer --- */
 .site-footer {
   border-top: 1px solid var(--border);