refactor: rename thumbnail_rendering queue to asset_pipeline

The queue handles far more than thumbnails: OCC tessellation, USD master
generation, GLB production, order line renders, and workflow renders.
asset_pipeline better reflects its role as the render-worker's primary queue.

Updated all references in: task decorators, celery_app.py, beat_tasks.py,
docker-compose.yml worker command, worker.py MONITORED_QUEUES, admin.py,
CLAUDE.md, LEARNINGS.md, Dockerfile, helpTexts.ts, test files,
and all .claude/commands/*.md skill files.

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

backend/app/api/routers/orders.py

@@ -1000,6 +1000,53 @@ async def cancel_line_render(
     }
 
 
+class RejectLineBody(BaseModel):
+    reason: str = ""
+
+
+@router.post("/{order_id}/lines/{line_id}/reject", status_code=200)
+async def reject_order_line(
+    order_id: uuid.UUID,
+    line_id: uuid.UUID,
+    body: RejectLineBody,
+    user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    """Reject a single order line (admin/PM only).
+
+    Sets item_status to 'rejected' and stores the reason in the notes field.
+    """
+    if not _is_privileged(user):
+        raise HTTPException(status_code=403, detail="Insufficient permissions")
+
+    result = await db.execute(select(Order).where(Order.id == order_id))
+    order = result.scalar_one_or_none()
+    if not order:
+        raise HTTPException(404, detail="Order not found")
+
+    line_result = await db.execute(
+        select(OrderLine).where(OrderLine.id == line_id, OrderLine.order_id == order_id)
+    )
+    line = line_result.scalar_one_or_none()
+    if not line:
+        raise HTTPException(404, detail="Order line not found")
+
+    from sqlalchemy import update as sql_update
+
+    notes_value = body.reason.strip() if body.reason and body.reason.strip() else line.notes
+    await db.execute(
+        sql_update(OrderLine)
+        .where(OrderLine.id == line.id)
+        .values(
+            item_status="rejected",
+            notes=notes_value,
+        )
+    )
+    await db.commit()
+
+    return {"rejected": True, "line_id": str(line.id), "reason": body.reason}
+
+
 @router.post("/{order_id}/cancel-renders")
 async def cancel_order_renders(
     order_id: uuid.UUID,