feat(precedent-library): add district and chair_name to edit form

Fields existed in DB and Precedent type but were missing from:
- PrecedentUpdateRequest (backend model)
- update_case_law allowed set (db layer)
- PrecedentPatch (frontend type)
- precedent-edit-sheet form state, inputs, and patch payload

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

web/app.py

@@ -4287,6 +4287,8 @@ class PrecedentUpdateRequest(BaseModel):
     source_type: str | None = None
     precedent_level: str | None = None
     is_binding: bool | None = None
+    district: str | None = None
+    chair_name: str | None = None
 
 
 class HalachaUpdateRequest(BaseModel):