refactor : migrate VERSION file to config/version.yaml

Same versioning system as SIRH/Lesstime. Updates nuxt.config.ts,
Dockerfile, deploy.sh, auto-tag CI, and release script.

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

deploy/docker/deploy.sh

@@ -24,5 +24,5 @@ echo "==> Clearing cache..."
 sudo docker compose exec -T -u www-data app php bin/console cache:clear --env=prod
 sudo docker compose exec -T -u www-data app php bin/console cache:warmup --env=prod
 
-VERSION=$(sudo docker compose exec -T app cat VERSION)
+VERSION=$(sudo docker compose exec -T app cat config/version.yaml | grep 'app.version' | awk -F"'" '{print $2}')
 echo "==> Deployed v${VERSION}"