fix: require Docker Compose v2 in scripts and docs

compose 1.29.2 aborts with KeyError: 'ContainerConfig' against Docker 28,
which broke the deploy on the prod VM.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/install.sh

@@ -8,7 +8,7 @@ REPO_URL="https://github.com/YOUR_ORG/YOUR_REPO.git"  # TODO: replace with actua
 
 echo "=== [1/6] Installing Docker and dependencies ==="
 apt-get update -qq
-apt-get install -y docker.io docker-compose-plugin git curl
+apt-get install -y docker.io docker-compose-v2 git curl
 
 echo "=== [2/6] Enabling Docker ==="
 systemctl enable --now docker
@@ -40,7 +40,7 @@ else
 fi
 
 echo "=== [6/6] Starting containers ==="
-docker-compose up -d
+docker compose up -d
 
 echo ""
 echo "=========================================="
@@ -49,5 +49,5 @@ echo " Health check: curl http://localhost:8082/health"
 echo ""
 echo " IMPORTANT: Edit ${PROXY_DIR}/.env"
 echo "   - Set DOMAIN, ACME_EMAIL and ALLOWED_CIDR"
-echo "   - Then run: docker-compose up -d"
+echo "   - Then run: docker compose up -d"
 echo "=========================================="