feat(ownership): complete ownership intelligence module

Sprints 0-8: Types, schema, KSEI parser, entity resolution, DB CRUD,
Bing API client, import pipeline, query commands, graph traversal,
changes diff, entity resolution CLI, FTS5 search.

- KSEI PDF parser (mutool stext + quick-xml, 99.2% accuracy)
- 7 query commands: ticker, entity, search, cross-holders, concentration, flow, releases
- Ownership graph with recursive CTE (ASCII tree + Graphviz DOT)
- Release diff/changes between KSEI snapshots
- Entity resolution CLI: unresolved, map, merge
- FTS5 trigram search on entity names
- Feature-gated under 'ownership' (default-on)
- 82 tests passing

flake.nix

@@ -29,6 +29,7 @@
             cargo-nextest
             prek
             curl-impersonate  # required for Yahoo Finance auth (curl_chrome* binaries for TLS fingerprinting)
+            mupdf             # mutool for KSEI PDF parsing (ownership module)
           ];
 
           env = {