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>

update.sh

@@ -152,7 +152,6 @@ Usage: $0 [options]
 
 Options:
   --multitenant      Use docker-compose-multitenant.yml (default)
-  --singletenant     Use docker-compose.yml
   -h, --help         Show this help message
 EOF
 }
@@ -164,10 +163,6 @@ parse_args() {
                 COMPOSE_FILE="docker-compose-multitenant.yml"
                 shift
                 ;;
-            --singletenant)
-                COMPOSE_FILE="docker-compose.yml"
-                shift
-                ;;
             -h|--help)
                 usage
                 exit 0