Feature/stream all backend steps

[AjayKumbham]

Summary

Implements real-time streaming of every backend process step to the frontend, as required by #5.

Details

• Backend now yields a structured event for every major step in the chat/memory/agent pipeline.
• Frontend (ChatOverlay) displays a live progress log of all backend steps above the chat bubbles.
• No breaking changes introduced.

Closes

Closes #5

CLA

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