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>

package.json

@@ -21,16 +21,21 @@
     "fix:prettier": "prettier -w ."
   },
   "dependencies": {
+    "@astrojs/react": "^4.4.2",
     "@astrojs/rss": "^4.0.11",
     "@astrojs/sitemap": "^3.3.0",
     "@astrolib/analytics": "^0.6.1",
     "@astrolib/seo": "^1.0.0-beta.8",
     "@fontsource-variable/inter": "^5.2.5",
+    "@types/react": "^19.2.8",
+    "@types/react-dom": "^19.2.3",
     "astro": "^5.7.3",
     "astro-embed": "^0.9.0",
     "astro-icon": "^1.1.5",
     "limax": "4.1.0",
     "lodash.merge": "^4.6.2",
+    "react": "^19.2.3",
+    "react-dom": "^19.2.3",
     "unpic": "^4.1.2"
   },
   "devDependencies": {