fix(chat): Resolve knowledge card display and section regeneration bugs

Created by: Edouard-Legoupil

This commit addresses two distinct issues in the Chat.jsx component and the backend API:

1. Display All Outcome Knowledge Cards: The logic for fetching and displaying knowledge cards associated with multiple outcomes has been corrected in Chat.jsx. Previously, URLSearchParams was used incorrectly, preventing multiple outcome_ids from being sent to the backend. The code has been updated to manually construct the query string, ensuring all relevant knowledge cards are fetched and displayed.

2. Fix Section Regeneration: The section regeneration feature was failing with a 400 Bad Request error because the temporary session created for the regeneration process was missing the proposal_template. The /regenerate_section/{proposal_id} endpoint in backend/api/proposals.py has been modified to load the proposal's template from the database and include it in the temporary Redis session. This resolves the error and restores the functionality.

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