feat: add about, contact with map, legal pages and 404

- About page with identity cards and equipment lists (about.json)
- Contact page: station info, obfuscated e-mail, lazy Leaflet/OSM map
  with antenna tower marker and dark-mode tiles
- Privacy, license and disclaimer pages from a legal collection
- QRT-themed 404 page
- LICENSE (MIT) and LICENSE-CONTENT (CC BY-SA 4.0 legal code)
- Shared PageHeader and CodeCopy components

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/styles/global.css

@@ -200,6 +200,10 @@
 .code-block {
   position: relative;
 }
+/* Room for the copy button so it never covers the first line. */
+.code-block > pre {
+  padding-top: 2.5rem;
+}
 .code-copy {
   position: absolute;
   top: 0.5rem;
@@ -217,3 +221,49 @@
   background: var(--accent-fill);
   color: var(--on-accent-fill);
 }
+
+/* ---------- Contact map (Leaflet) ---------- */
+.tower-marker {
+  background: none;
+  border: 0;
+}
+/* Rotate an inner element: `rotate` on the marker itself would also rotate Leaflet's translate3d. */
+.tower-pin {
+  display: flex;
+  width: 100%;
+  height: 100%;
+  align-items: center;
+  justify-content: center;
+  background: var(--accent-fill);
+  color: var(--on-accent-fill);
+  border: 2px solid var(--fg);
+  border-radius: 50% 50% 50% 0;
+  rotate: -45deg;
+}
+.tower-pin svg {
+  rotate: 45deg;
+}
+.leaflet-container .leaflet-control-attribution {
+  background: var(--surface);
+  color: var(--fg);
+}
+.leaflet-container .leaflet-control-attribution a {
+  color: var(--accent-strong);
+}
+.leaflet-container {
+  font: inherit;
+  background: var(--bg-alt);
+}
+.leaflet-popup-content {
+  font-family: var(--font-display);
+  font-weight: 700;
+}
+/* Dark tiles without a second tile provider. */
+[data-theme='dark'] .leaflet-tile-pane {
+  filter: invert(1) hue-rotate(180deg) brightness(0.85) contrast(0.9);
+}
+.leaflet-container .leaflet-popup-content-wrapper,
+.leaflet-container .leaflet-popup-tip {
+  background: var(--surface);
+  color: var(--fg);
+}