remove: delete corrupted rename-app.sh file and update references

- Remove rename-app.sh which contains corrupted deployment validation content
- File was misnamed (should be deployment validation, not app renaming)
- Contains broken/mixed content and isn't relevant for current development
- App is not deployed to production yet, so deployment validation scripts aren't needed
- Update SECURITY_CHANGES.md to remove references to deleted file

docs/development/SECURITY_CHANGES.md

@@ -28,7 +28,6 @@ Updated all deployment and build scripts with secure password fallbacks:
 - `scripts/gitea-deploy.sh`
 - `scripts/gitea-helper.sh`
 - `scripts/seed-production.js`
-- `rename-app.sh`
 
 ### 4. CI/CD Workflows
 
@@ -119,7 +118,6 @@ Updated all deployment and build scripts with secure password fallbacks:
 - `scripts/gitea-deploy.sh`
 - `scripts/gitea-helper.sh`
 - `scripts/seed-production.js`
-- `rename-app.sh`
 
 ### Documentation (5)