REFACTOR(app): migrate to argocd

- Add Kustomize base and prod overlay structure
- Optimize resources for 2GB RAM environment (100Mi/200Mi)
- Add ArgoCD Application manifest
- Remove old k8s manifests (replaced by Kustomize)
- Add comprehensive deployment guide

.github/workflows/build.yml

@@ -72,3 +72,6 @@ jobs:
           echo "📦 Image tags:"
           echo "${{ steps.meta.outputs.tags }}"
           echo "🔖 Digest: ${{ steps.build.outputs.digest }}"
+          echo ""
+          echo "🚀 ArgoCD will automatically detect and deploy this new image"
+          echo "   Monitor deployment at your ArgoCD dashboard"