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>

public/admin/config.yml

@@ -21,7 +21,7 @@ site_url: https://radio.org.tr
 display_url: https://radio.org.tr
 
 # Logo for admin login page
-logo_url: https://radio.org.tr/_astro/ARC_2024_bayrak_logo-Large-1-1024x1024.png
+logo_url: https://radio.org.tr/images/ARC_2024_bayrak_logo-Large-1-1024x1024.png
 
 collections:
   - name: 'post'