Remove legacy scripts and single-tenant support

- Deleted the migration script `migrate-to-multitenant.sh` as it is no longer needed.
- Removed `rebuild-venv.sh`, `restore.sh`, `run-backup.sh`, and other related scripts that are not compatible with the new multi-tenant architecture.
- Updated `restart.sh`, `start.sh`, `stop.sh`, `update.sh`, and other scripts to eliminate references to single-tenant deployment, ensuring they only support multi-tenant configurations.

Co-authored-by: Copilot <copilot@github.com>

stop.sh

@@ -12,10 +12,6 @@ while [[ $# -gt 0 ]]; do
             COMPOSE_FILE="docker-compose-multitenant.yml"
             shift
             ;;
-        --singletenant)
-            COMPOSE_FILE="docker-compose.yml"
-            shift
-            ;;
         *)
             shift
             ;;