Implement Astro features: React Islands, Server Endpoints, i18n, Partytown

Features added:
- React integration with @astrojs/react
- React components: DMRDashboard, MemberSearch
- API endpoints: /api/repeaters.json, /api/dmr-contacts.json, /api/feed/[category].xml
- i18n support for TR/EN locales with LanguageSwitcher component
- Partytown enabled for third-party script optimization
- Admin panel logo fixed (moved to public/images/)

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

src/components/LanguageSwitcher.astro

@@ -0,0 +1,27 @@
+---
+const { currentLocale } = Astro.params;
+const locales = ['tr', 'en'];
+const path = Astro.url.pathname;
+
+function getLocalePath(locale: string) {
+  // Remove locale prefix from current path
+  const cleanPath = path.replace(/^\/(tr|en)\//, '/');
+  return locale === 'tr' ? cleanPath : `/en${cleanPath}`;
+}
+---
+
+<div class="flex items-center gap-2">
+  {locales.map(locale => (
+    <a
+      href={getLocalePath(locale)}
+      class={`px-3 py-1 rounded-lg text-sm font-medium transition-colors ${
+        currentLocale === locale
+          ? 'bg-blue-600 text-white'
+          : 'bg-gray-200 text-gray-700 hover:bg-gray-300'
+      }`}
+      aria-label={`Switch to ${locale === 'tr' ? 'Turkish' : 'English'}`}
+    >
+      {locale === 'tr' ? 'TR' : 'EN'}
+    </a>
+  ))}
+</div>