Redesign admin Infra page: full-screen 4-column layout with Docker stats

Complete rewrite of /admin/infra into 4 columns:
- Col 1 (Serveur): CPU, RAM, Disk, System, Services (Caddy, Docker, SSL cert)
- Col 2 (Containers): All Docker containers with CPU%, RAM, state via Docker API
- Col 3 (Redis): Global stats + per-DB (Messenger, Sessions, Cache)
- Col 4 (PostgreSQL): Instance stats + PgBouncer pools/stats

Extract all infra logic into InfraService. Mount Docker socket (read-only)
in PHP container for container stats. Check SSL cert expiry and Caddy status.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker-compose-dev.yml

@@ -7,6 +7,7 @@ services:
     restart: unless-stopped
     volumes:
       - .:/app
+      - /var/run/docker.sock:/var/run/docker.sock:ro
     ports:
       - "9000:9000"
     depends_on: