Add production CI/CD deployment pipeline

Add GHCR image build/push and SSH-based server deployment workflow, production compose/env templates, and deployment script. Also fix frontend container healthcheck target and extend Docker CI with frontend health verification.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.github/workflows/docker.yml

@@ -19,13 +19,17 @@ jobs:
 
       - name: Start services
         run: |
-          docker compose -f devops/docker-compose.yml up -d db backend
-          sleep 15
+          docker compose -f devops/docker-compose.yml up -d db backend frontend
+          sleep 30
 
       - name: Verify backend health
         run: |
           docker compose -f devops/docker-compose.yml exec -T backend node -e "const h=require('http');h.get('http://localhost:5000/health',(r)=>{let d='';r.on('data',c=>d+=c);r.on('end',()=>{console.log(d);process.exit(r.statusCode===200?0:1)})}).on('error',e=>{console.error(e);process.exit(1)})"
 
+      - name: Verify frontend health
+        run: |
+          curl -fsS http://localhost:3000 >/dev/null
+
       - name: Cleanup
         if: always()
         run: docker compose -f devops/docker-compose.yml down -v