Consolidate backup storage to single mongo-backup directory

- Unify all backup scripts to use ./mongo-backup/ directory
- Update db-backup--standalone.sh to store volume backups in mongo-backup/
- Update db-backup--swarm.sh to use mongo-backup as default directory
- Update db-restore-from-backup--swarm.sh to look in mongo-backup/
- Update all header comments and documentation to reflect new location
- Update .gitignore to ignore both backups/ and mongo-backup/
- Update README.md with consolidated backup directory paths

This simplifies backup management by having all backup types in one location.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

db-backup--swarm.sh

@@ -21,7 +21,7 @@ set -euo pipefail
 #   - Creates compressed tarball (.tar.gz) of the volume
 #
 # OUTPUT:
-#   - Backup files stored in: ./backups/
+#   - Backup files stored in: ./mongo-backup/
 #   - Filename format: mongo-volume-backup-YYYY-MM-DD-HH-MM.tar.gz
 #   - Automatic rotation: keeps newest 7 backups (configurable via KEEP env var)
 #
@@ -45,7 +45,7 @@ docker service scale "$MONGO_SERVICE"=0
 TIMESTAMP=$(date +"%Y-%m-%d-%H-%M")
 
 # backup directory and retention (can be overridden via env)
-BACKUP_DIR="${BACKUP_DIR:-backups}"
+BACKUP_DIR="${BACKUP_DIR:-mongo-backup}"
 KEEP="${KEEP:-7}"
 
 mkdir -p "$BACKUP_DIR"