Get Citation Edge Paragraphs

Paragraphs in the citing case that cite the cited case.

Backs the citation-graph edge click: an edge is a directed citing→cited relationship, so this returns every paragraph of the citing judgment that references the cited authority, with the paragraph text. Falls back to resolving the text from full_text when no chunk row exists.

Reads the authority_citation_edges view — the same surface the graph is drawn from — so tribunal-ref appeal edges (which don't exist in authority_citations) return their paragraphs instead of an empty drawer.

A plain def (not async): the sync DB fetches, regex extraction and per-occurrence resolution run in FastAPI's threadpool rather than blocking the event loop (matching the sibling get_citing_paragraphs).