feat: build home page from home.json sections

- Hero with callsign/locator tags and CTAs on khaki grid
- Feature sections for ARD (YM1KTC), DMR Türkiye, QRV73!, QRZ73!
- Telegram groups and resource site card grids
- Latest posts block with empty state (wired to blog in stage 4)
- Section wrapper, decorative numerals, external Button variant

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

src/components/home/CardGrid.astro

@@ -0,0 +1,51 @@
+---
+import { Icon } from 'astro-icon/components';
+import type { HomeSection } from '../../lib/data';
+import Card from '../Card.astro';
+import ExternalLink from '../ExternalLink.astro';
+import Section from '../Section.astro';
+import SectionHeading from '../SectionHeading.astro';
+
+export interface Props {
+  section: Extract<HomeSection, { type: 'cards' }>;
+  alt: boolean;
+}
+
+const { section, alt } = Astro.props;
+const headingId = `${section.id}-title`;
+const display = (href: string) => {
+  const u = new URL(href);
+  return (u.host + u.pathname).replace(/^www\./, '').replace(/\/$/, '');
+};
+---
+
+<Section id={section.id} alt={alt} labelledby={headingId}>
+  <SectionHeading id={headingId} eyebrow={section.eyebrow} title={section.title} />
+  <ul class="mt-10 grid gap-6 sm:grid-cols-2 lg:grid-cols-3">
+    {section.items.map((item) => (
+      <li class="flex">
+        <Card interactive class="w-full">
+          <div class="flex flex-1 flex-col gap-4 p-6">
+            <span class="bg-bg-alt text-fg inline-flex size-12 items-center justify-center">
+              <Icon name={item.icon} class="size-6" aria-hidden="true" />
+            </span>
+            <h3 class="text-xl leading-snug font-bold">
+              <ExternalLink
+                href={item.href}
+                icon={false}
+                class="after:absolute after:inset-0 hover:underline"
+              >
+                {item.title}
+              </ExternalLink>
+            </h3>
+            {item.description && <p class="text-fg-muted text-sm">{item.description}</p>}
+            <p class="text-accent-text mt-auto inline-flex items-center gap-1 text-sm font-semibold">
+              {display(item.href)}
+              <Icon name="tabler:external-link" class="size-4" aria-hidden="true" />
+            </p>
+          </div>
+        </Card>
+      </li>
+    ))}
+  </ul>
+</Section>