Fix court case detail API error - remove nonexistent dissent_author field

The API router and schema referenced a dissent_author field that doesn't
exist in the database model or table. This caused 500 errors when viewing
case detail pages (e.g., /cases/1).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: sfbaytides

src/civitas/api/routers/cases.py

@@ -111,7 +111,6 @@ async def get_case(
         docket_number=case.docket_number,
         holding=case.holding,
         majority_author=case.majority_author,
-        dissent_author=case.dissent_author,
         source_url=case.source_url,
         linked_objectives=[objective_to_base(obj) for obj in linked_objectives],
         **insight,

src/civitas/api/schemas.py

@@ -239,7 +239,6 @@ class CourtCaseDetail(CourtCaseBase):
     docket_number: str | None = None
     holding: str | None = None
     majority_author: str | None = None
-    dissent_author: str | None = None
     source_url: str | None = None
     linked_objectives: list[ObjectiveBase] = []
     plain_summary: str | None = None