LLM prompts updated to output {text, citation, quote} objects for every
key_point and risk. govinfo_url stored on BillBrief (migration 0006) so
the frontend can link directly to the source document without an extra
query. AIBriefCard renders § citation chips that expand inline to show
the verbatim quote and a View source → GovInfo link. Old plain-string
briefs continue to render unchanged.
Authored-By: Jack Levy
