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/content.config.ts

@@ -30,4 +30,14 @@ const blog = defineCollection({
       }),
 });
 
-export const collections = { blog };
+// Legal pages: src/content/legal/<slug>.md → /<slug>/
+const legal = defineCollection({
+  loader: glob({ pattern: '*.md', base: './src/content/legal' }),
+  schema: z.object({
+    title: z.string().max(60),
+    description: z.string().min(50).max(160),
+    updated: z.coerce.date(),
+  }),
+});
+
+export const collections = { blog, legal };