Backend startup fails due to mixed Weaviate client APIs (v3 vs v4)

While setting up and running the backend locally as a contributor, I encountered runtime errors related to the Weaviate Python client that appear to stem from mixed usage of different major Weaviate client APIs within the codebase.

Specifically:

Some modules rely on v3-style imports (e.g. from weaviate import classes)

Other modules expect v4-style APIs (e.g. WeaviateClient)

Because of this, the backend fails to start consistently in a clean environment:

Installing a v3 client resolves classes imports but breaks WeaviateClient

Installing a v4 client resolves WeaviateClient but breaks classes

Steps to Reproduce :
1.Create a fresh Python virtual environment
2.Install backend dependencies
3.Run python backend/main.
4.Observe import / attribute errors related to the Weaviate client
5.Observed Errors
- ImportError: cannot import name 'classes' from weaviate
- AttributeError: module 'weaviate' has no attribute 'WeaviateClient'

Expected Behavior

The backend should consistently target a single Weaviate client major version, with aligned imports and dependency pinning, so that it can start successfully in a clean setup.

Notes :
Resolving this likely requires a maintainer decision on whether to standardize the backend on:
Weaviate client v3 (legacy), or
Weaviate client v4 (current).

Happy to help further once the preferred direction is clarified.