[Feature Request]: Enhance WebUI Streaming Response Support

[danielaskdd]

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Feature Request Description

The WebUI's query functionality does not adequately support streaming responses. The following improvements are needed:

1. When selecting streaming responses for queries, the WebUI should process LightRAG's responses according to streaming response specifications.
2. Switching tabs during a streaming response should not interrupt the response (currently, tab switching only hides the page and should not require special handling).
3. Only session history should be maintained. The session history should be stored in the backend.

Additional Context

No response

[danielaskdd]

Session history is not implemented.