Merge deploy playbooks, add env.local template, update MailerService

- Fuse deploy-caddy.yml and cloudflare.yml into deploy.yml
- Add env.local.j2 template for production secrets
- Vault: add all production secrets
- Workflow: single deploy.yml playbook
- MailerService: rewrite with S/MIME signing, email tracking, unsubscribe
- ngrok-sync: run as root for .env.local write access
- Fix domain references to ticket.e-cosplay.fr

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

docker-compose-dev.yml

@@ -130,6 +130,7 @@ services:
   ngrok-sync:
     image: curlimages/curl:latest
     container_name: e_ticket_ngrok_sync
+    user: "0:0"
     volumes:
       - .:/app
       - ./docker/ngrok/sync.sh:/sync.sh