Add RetainPolicyEnum and retain_policy config field for NVR-style storage

Introduce a new RetainPolicyEnum with 'time' (default, existing behavior)
and 'continuous_rollover' (fill disk, overwrite oldest) options. Add the
retain_policy field to RecordConfig and include unit tests for config
validation.

frigate/config/camera/record.py

@@ -17,6 +17,7 @@ __all__ = [
     "ReviewRetainConfig",
     "RecordRetainConfig",
     "RetainModeEnum",
+    "RetainPolicyEnum",
 ]
 
 
@@ -35,6 +36,11 @@ class RetainModeEnum(str, Enum):
     active_objects = "active_objects"
 
 
+class RetainPolicyEnum(str, Enum):
+    time = "time"
+    continuous_rollover = "continuous_rollover"
+
+
 class ReviewRetainConfig(FrigateBaseModel):
     days: float = Field(
         default=10,
@@ -100,6 +106,11 @@ class RecordConfig(FrigateBaseModel):
         title="Enable recording",
         description="Enable or disable recording for all cameras; can be overridden per-camera.",
     )
+    retain_policy: RetainPolicyEnum = Field(
+        default=RetainPolicyEnum.time,
+        title="Retention policy",
+        description="Storage retention policy. 'time' expires recordings after configured days. 'continuous_rollover' fills available disk space and overwrites oldest recordings when space is needed.",
+    )
     expire_interval: int = Field(
         default=60,
         title="Record cleanup interval",

frigate/test/test_config_retain_policy.py

@@ -0,0 +1,49 @@
+import unittest
+
+from frigate.config import FrigateConfig
+
+
+class TestRetainPolicyConfig(unittest.TestCase):
+    def setUp(self):
+        self.base_config = {
+            "mqtt": {"host": "mqtt"},
+            "cameras": {
+                "front_door": {
+                    "ffmpeg": {
+                        "inputs": [
+                            {"path": "rtsp://10.0.0.1:554/video", "roles": ["detect"]}
+                        ]
+                    },
+                    "detect": {"height": 1080, "width": 1920, "fps": 5},
+                }
+            },
+        }
+
+    def test_default_retain_policy_is_time(self):
+        config = FrigateConfig(**self.base_config)
+        assert config.record.retain_policy.value == "time"
+
+    def test_continuous_rollover_policy(self):
+        self.base_config["record"] = {
+            "enabled": True,
+            "retain_policy": "continuous_rollover",
+        }
+        config = FrigateConfig(**self.base_config)
+        assert config.record.retain_policy.value == "continuous_rollover"
+
+    def test_continuous_rollover_ignores_continuous_days(self):
+        self.base_config["record"] = {
+            "enabled": True,
+            "retain_policy": "continuous_rollover",
+            "continuous": {"days": 30},
+        }
+        config = FrigateConfig(**self.base_config)
+        assert config.record.retain_policy.value == "continuous_rollover"
+        assert config.record.continuous.days == 30
+
+    def test_invalid_retain_policy_rejected(self):
+        self.base_config["record"] = {
+            "retain_policy": "invalid_value",
+        }
+        with self.assertRaises(Exception):
+            FrigateConfig(**self.base_config)