chore: update backup configurations and directory structure

- Modified `.gitignore` to exclude all files in the `/data/` directory.
- Enhanced `BACKUP.md` with customization options for backup storage paths and updated database path configurations.
- Updated `docker-compose.yml` to reflect new paths for database and backup storage.
- Adjusted `Dockerfile` to create a dedicated backups directory.
- Refactored `BackupService` to utilize environment variables for backup paths, improving flexibility and reliability.
- Deleted `dev.db` as it is no longer needed in the repository.

env.example

@@ -1,5 +1,13 @@
 # Base de données (requis)
-DATABASE_URL="file:./dev.db"
+DATABASE_URL="file:../data/dev.db"
+
+# Chemin de la base de données pour les backups (optionnel)
+# Si non défini, utilise DATABASE_URL ou le chemin par défaut
+BACKUP_DATABASE_PATH="./data/dev.db"
+
+# Dossier de stockage des sauvegardes (optionnel)
+# Par défaut: ./backups en local, ./data/backups en production
+BACKUP_STORAGE_PATH="./backups"
 
 # Intégration Jira (optionnel)
 JIRA_BASE_URL=""                    # https://votre-domaine.atlassian.net