exclude maintenance.flag from rsync deploy and git

TODO.md

@@ -97,3 +97,4 @@
 - [x] Replace old button definitions in admin.css, form.css, tfe.css, file-access.css, system.css with empty alias comments
 - [x] Update all PHP templates to use new `.btn` classes (`btn btn--primary`, `btn btn--secondary`, `btn btn--danger`, etc.)
 - [x] Update border-radius on pagination buttons to 10px for consistency
+- [x] Exclude `storage/maintenance.flag` from rsync deploy and git