Add naming scheme selection to run configuration

Add a nullable naming_scheme column to NuzlockeRun so users can pick a
themed word category for nickname suggestions. Includes Alembic migration,
updated Pydantic schemas, a GET /runs/naming-categories endpoint backed by
a cached dictionary loader, and frontend dropdowns in both the NewRun
creation flow and the RunDashboard for mid-run changes.

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

backend/src/app/api/runs.py

@@ -19,10 +19,16 @@ from app.schemas.run import (
     RunResponse,
     RunUpdate,
 )
+from app.services.naming import get_naming_categories
 
 router = APIRouter()
 
 
+@router.get("/naming-categories", response_model=list[str])
+async def list_naming_categories():
+    return get_naming_categories()
+
+
 @router.post("", response_model=RunResponse, status_code=201)
 async def create_run(data: RunCreate, session: AsyncSession = Depends(get_session)):
     # Validate game exists
@@ -35,6 +41,7 @@ async def create_run(data: RunCreate, session: AsyncSession = Depends(get_sessio
         name=data.name,
         status="active",
         rules=data.rules,
+        naming_scheme=data.naming_scheme,
     )
     session.add(run)
     await session.commit()