REFACTOR(repo): simplify project structure

- Move services/nextjs/ to nextjs/
- Move Dockerfile.prod to Dockerfile at root
- Remove deploy/ folder (K8s manifests moved to K3S-HOME/web-apps)
- Remove .gitea/ workflows
- Update GitHub Actions for new structure
- Remove develop branch triggers

nextjs/components/ui/language-toggle.tsx

@@ -0,0 +1,58 @@
+'use client';
+
+import * as React from 'react';
+import { Languages } from 'lucide-react';
+import { Button } from '@/components/ui/button';
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuItem,
+  DropdownMenuTrigger,
+} from '@/components/ui/dropdown-menu';
+import { usePathname, useRouter } from '@/i18n/routing';
+import { useParams } from 'next/navigation';
+
+const LANGUAGES = [
+  { code: 'ko', name: '한국어', flag: '🇰🇷' },
+  { code: 'en', name: 'English', flag: '🇺🇸' },
+  { code: 'de', name: 'Deutsch', flag: '🇩🇪' },
+];
+
+export function LanguageToggle() {
+  const router = useRouter();
+  const pathname = usePathname();
+  const params = useParams();
+  const currentLocale = params.locale as string;
+
+  const handleLanguageChange = (locale: string) => {
+    router.replace(pathname, { locale: locale as any });
+  };
+
+  const currentLanguage = LANGUAGES.find(lang => lang.code === currentLocale) || LANGUAGES[0];
+
+  return (
+    <DropdownMenu>
+      <DropdownMenuTrigger asChild>
+        <Button variant="ghost" size="icon" className="ml-2">
+          <Languages className="h-[1.2rem] w-[1.2rem]" />
+          <span className="sr-only">Toggle language</span>
+        </Button>
+      </DropdownMenuTrigger>
+      <DropdownMenuContent align="end">
+        {LANGUAGES.map((language) => (
+          <DropdownMenuItem
+            key={language.code}
+            onClick={() => handleLanguageChange(language.code)}
+            className="cursor-pointer"
+          >
+            <span className="mr-2">{language.flag}</span>
+            {language.name}
+            {currentLanguage.code === language.code && (
+              <span className="ml-2">✓</span>
+            )}
+          </DropdownMenuItem>
+        ))}
+      </DropdownMenuContent>
+    </DropdownMenu>
+  );
+}