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/about-us/page.tsx

@@ -0,0 +1,3 @@
+export default function AboutUs(){
+    return <div>Practice app for K8s/argoCD/Grafana</div>
+}