feat: Add support for Time-weighted vector store retriever

[hiro-v]

Problem

• In long conversation especially with file uploaded, it's likely that the LLM cannot remember the conversational history which is long away (underlying this exceeds LLM context window).

Success Criteria

• Add support for https://js.langchain.com/docs/modules/data_connection/retrievers/time_weighted_vectorstore in https://github.com/janhq/jan/blob/dev/extensions/assistant-extension/src/node/tools/retrieval/index.ts#L66

Additional context

[thunhuanh]

Can I pick up this issue? @hiro-v @louis-jan