Creating the same project more than once with the same URL allows duplicate creation

[Naseem77]

Description:
When attempting to create a project with a URL that already exists in the system, the application does not prevent the creation of a duplicate project. There is no validation to check for URL uniqueness, allowing multiple projects to be created with the same URL, which can lead to confusion or potential routing issues.

Steps to Reproduce:

1. Navigate to code graph home page
2. Click create project
3. Insert project URL: "https://github.com/FalkorDB/GraphRAG-SDK"
4. Attempt to create another project using the same URL ("https://github.com/FalkorDB/GraphRAG-SDK").
5. Observe that the second project is created successfully with the same URL.