fix: COMPOSE_DIR corrigé dans gitea-auto-update.sh + credentials paramétrés

- COMPOSE_DIR aligné sur le vrai chemin (~/dev/git/outils/docker/gitea)
- Backup pré-update utilise DB_CONTAINER/DB_ROOT_PASSWORD/DB_NAME
- Ajout set -euo pipefail dans backup-docker.sh

backup-docker.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+set -euo pipefail
+
+BACKUP_DIR="/NFS/BACKUPS"
+DATE=$(date +%Y%m%d)
+mkdir -p $BACKUP_DIR
+
+docker run --rm -v jellyfin_data:/source -v $BACKUP_DIR:/backup alpine \
+  tar czf /backup/jellyfin-$DATE.tar.gz /source
+docker run --rm -v shaarli_data:/source -v $BACKUP_DIR:/backup alpine \
+  tar czf /backup/shaarli-$DATE.tar.gz /source
+
+# Vérification
+ls -lh $BACKUP_DIR | grep -E "jellyfin|shaarli"