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/app/api/health/route.ts

@@ -0,0 +1,25 @@
+import { NextResponse } from 'next/server'
+import { prisma } from '@/shared/lib/prisma'
+
+export async function GET() {
+  try {
+    // 데이터베이스 연결 확인
+    await prisma.$queryRaw`SELECT 1`
+    
+    return NextResponse.json({
+      status: 'ok',
+      timestamp: new Date().toISOString(),
+      database: 'connected'
+    })
+  } catch {
+    return NextResponse.json(
+      {
+        status: 'error',
+        timestamp: new Date().toISOString(),
+        error: 'Database connection failed'
+      },
+      { status: 503 }
+    )
+  }
+}
+