Add conflict-of-interest check engine; gate stage advancement at Intake

- New fl.conflict.check model: screens petitioner/respondent/party_ids names
  against parties on other open cases (exact partner match + difflib fuzzy
  match at 0.85 threshold); skips folded/closed stages
- Runs automatically as the first action in fl.case.create; logs conflicts to
  chatter with matched-case detail and never silently passes
- fl.case gains conflict_check_passed/conflict_check_id/conflict_check_ids;
  write() blocks advancing stage_id past Intake until the check passes
- Admin-only action_override requires a written justification, stamps user/date,
  and flips conflict_check_passed True with a chatter audit entry
- Add conflict check form/tree/search views, action, Cases sub-menu item,
  case form banner + Run Conflict Check button, and Kanban conflict badge
- ACL entries for fl.conflict.check (admin full, paralegal no-delete)
- Finish Claude migration cleanup in fl_analysis.py (model_used default,
  docstring/help text)
- Add .gitignore for Python artifacts

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

activeblue_familylaw/models/__init__.py

@@ -15,3 +15,4 @@ from . import fl_analysis
 from . import fl_ai_engine
 from . import fl_argument
 from . import fl_case
+from . import fl_conflict_check