perf(track): add __slots__ to TrackedObjectAttribute

TrackedObjectAttribute is constructed per attribute (face, license plate,
logo, ...) per frame in process_frames. It holds exactly six fixed fields
and is never mutated beyond __init__, so __slots__ removes the per-instance
__dict__.

Measured in the release image: 352 B/instance (56 B object + 296 B __dict__)
-> ~104 B with __slots__, ~70% smaller, on a high-churn per-frame object.

Adds a test asserting no __dict__ and that undeclared attributes raise.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frigate/test/test_obects.py

@@ -3,6 +3,21 @@ import unittest
 from frigate.track.tracked_object import TrackedObjectAttribute
 
 
+class TestAttributeSlots(unittest.TestCase):
+    def test_attribute_uses_slots(self) -> None:
+        attribute = TrackedObjectAttribute(
+            ("amazon", 0.8, (847, 242, 883, 255), 468, 2.77, (702, 134, 1050, 482))
+        )
+        # __slots__ means no per-instance __dict__
+        self.assertFalse(hasattr(attribute, "__dict__"))
+        # all declared fields are still populated and readable
+        self.assertEqual(attribute.label, "amazon")
+        self.assertEqual(attribute.region, (702, 134, 1050, 482))
+        # setting an undeclared attribute must raise (catches accidental drift)
+        with self.assertRaises(AttributeError):
+            attribute.unexpected = 1
+
+
 class TestAttribute(unittest.TestCase):
     def test_overlapping_object_selection(self) -> None:
         attribute = TrackedObjectAttribute(

frigate/track/tracked_object.py

@@ -574,6 +574,8 @@ def zone_filtered(obj: TrackedObject, object_config: dict[str, FilterConfig]) ->
 
 
 class TrackedObjectAttribute:
+    __slots__ = ("label", "score", "box", "area", "ratio", "region")
+
     def __init__(self, raw_data: tuple) -> None:
         self.label = raw_data[0]
         self.score = raw_data[1]