Renames the backup script to match the instance, not the software

backup-slpmodularcms-db.sh named the CMS; this backs up slpsoftware
specifically, same as every other instance-scoped path already does.
Hardcoded in deploy-scp.yaml itself, so this is the actual pipeline
code, not just docs describing it.

.gitea/workflows/deploy-scp.yaml

@@ -64,7 +64,7 @@ jobs:
             -p ${{ secrets.PI_MAIN_PORT }} \
             -o StrictHostKeyChecking=no \
             ${{ secrets.PI_MAIN_USERNAME }}@${{ secrets.PI_MAIN_ADDRESS }} \
-            "bash ~/scripts/backup-slpmodularcms-db.sh ${{ inputs.environment }}"
+            "bash ~/scripts/backup-slpsoftware-db.sh ${{ inputs.environment }}"
 
       # Uploads the published output to a fresh, timestamped release directory rather than
       # overwriting the live one (FR-06, D-27) — the atomic switch happens in a later step, once