feat: live count worker, tracking, and page updates

backend/api/live_count.py

@@ -22,6 +22,7 @@ class StartRequest(BaseModel):
     source_rel: Optional[str] = None
     model_path: Optional[str] = None
     model_version_id: Optional[int] = None
+    count_classes: list = ["sack"]
     line_y: int = 266
     line_x_start: int = 469
     line_x_end: int = 910
@@ -97,6 +98,7 @@ def start(project_id: int, request: StartRequest) -> dict:
             min_area_scale=request.min_area_scale,
             spatial_dedup=request.spatial_dedup,
             whep=whep,
+            count_classes=tuple(request.count_classes),
         )
     except live_count.LiveCountError as exc:
         raise HTTPException(400, str(exc))