No Restriction on Duplicate Restaurant Names Under the Same Vendor

Describe the bug
Currently, the system allows creation of multiple restaurants with the same name under the same vendor account. This can lead to confusion, data conflicts, and operational issues. There is no validation or message indicating that the restaurant name already exists.

To Reproduce
Steps to reproduce the behavior:

Log in as a vendor

Create a restaurant/store with a specific name (e.g., "Tasty Bites")

Attempt to create another restaurant with the same name under the same vendor account

Observe that the system allows it without any warning or error

Expected behavior
There should be a restriction in place to prevent creating duplicate restaurant names under the same vendor. The system should display a clear validation message like:
"A restaurant with this name already exists."

Screenshots

Image

Desktop (please complete the following information):

OS: Windows 11

Browser: Chrome

Version: [e.g., 123.0.6312.86]

Additional context
This issue may affect order routing, reporting, and user management. Implementing this validation would help maintain data integrity and improve user experience for vendors managing multiple stores.

The issue names no files or tests. Start by tracing the restaurant creation flow and its vendor-scoped name validation, then add coverage for creating the same name twice under one vendor; done means the second creation is rejected with the specified message while identical names under different vendors remain possible.

Written by the indexing model from the issue text.