pin setuptools<81 to ensure pkg_resources remains available

When ensure_torch_dependencies() installs torch/torchvision via pip, it can upgrade setuptools to >=81.0.0, which removed the pkg_resources module. rknn-toolkit2 depends on pkg_resources internally, so subsequent RKNN conversion fails with No module named 'pkg_resources'.

frigate/util/rknn_converter.py

@@ -110,6 +110,7 @@ def ensure_torch_dependencies() -> bool:
                     "pip",
                     "install",
                     "--break-system-packages",
+                    "setuptools<81",
                     "torch",
                     "torchvision",
                 ],