Rename default staff roles: Manager, Support Staff, Staff

- Renamed "Full Access Staff" to "Manager"
- Renamed "Front Desk" to "Support Staff"
- Renamed "Limited Staff" to "Staff"
- Updated permissions: Support Staff now has access to messages and payments
- Updated all references in code, tests, help docs, and translations
- Added migration 0016 to rename existing roles in database

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/i18n/locales/en.json

@@ -1979,7 +1979,7 @@
       "deleteRole": "Delete Role",
       "roleName": "Role Name",
       "roleDescription": "Description",
-      "roleNamePlaceholder": "e.g., Front Desk",
+      "roleNamePlaceholder": "e.g., Support Staff",
       "roleDescriptionPlaceholder": "Brief description of this role's responsibilities",
       "permissions": "Permissions",
       "menuAccess": "Menu Access",