feat(devices): add DeviceHealthSettings model for per-device alert thresholds

Two-tier (warning/critical) threshold config per device — restarts/week,
RSSI floor, free-heap floor, CPU temp ceiling, plus an offline timeout
used for both a client-computed health status icon and the Health tab
chart's gap detection. Purely advisory for now: no server-side
email/push alerting infra exists yet, so email_on_threshold and
push_on_crash_boot are placeholders for that future work.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/devices/models.py

@@ -98,6 +98,35 @@ class DeviceStatistics(BaseModel):
     maintainancePeriod: int = 0
 
 
+class HealthThresholdTier(BaseModel):
+    """One severity tier's worth of metric thresholds. Two tiers (warning,
+    critical) make up DeviceHealthSettings — see there for why."""
+    restarts_per_week_threshold: int
+    rssi_floor_dbm: int
+    free_heap_floor_kb: int
+    cpu_temp_ceiling_c: int
+
+
+class DeviceHealthSettings(BaseModel):
+    """Per-device alert thresholds shown/edited on the Health tab's Settings
+    sub-tab. Purely advisory today — thresholds drive a client-computed
+    ok/warning/critical status icon, not any server-side alerting yet (no
+    email/push infra exists). Two severity tiers per metric (warning fires
+    first, critical is the harder breach) so the header status icon can show
+    orange vs. red rather than a single degraded/healthy binary.
+    offline_timeout_sec also feeds the Health tab's chart gap detection
+    (LineChart's gapThresholdMs) so both share one source of truth."""
+    warning: HealthThresholdTier = HealthThresholdTier(
+        restarts_per_week_threshold=6, rssi_floor_dbm=-80, free_heap_floor_kb=30, cpu_temp_ceiling_c=65,
+    )
+    critical: HealthThresholdTier = HealthThresholdTier(
+        restarts_per_week_threshold=12, rssi_floor_dbm=-90, free_heap_floor_kb=15, cpu_temp_ceiling_c=80,
+    )
+    offline_timeout_sec: int = 90
+    email_on_threshold: bool = False
+    push_on_crash_boot: bool = False
+
+
 class MelodyMainItem(BaseModel):
     """Mirrors the Melody schema used in the melodies collection."""
     information: dict = {}
@@ -118,6 +147,7 @@ class DeviceCreate(BaseModel):
     device_attributes: DeviceAttributes = DeviceAttributes()
     device_subscription: DeviceSubInformation = DeviceSubInformation()
     device_stats: DeviceStatistics = DeviceStatistics()
+    device_health_settings: DeviceHealthSettings = DeviceHealthSettings()
     events_on: bool = False
     device_location_coordinates: Any = None  # GeoPoint dict {lat, lng} or legacy str
     device_melodies_all: List[MelodyMainItem] = []
@@ -143,6 +173,7 @@ class DeviceUpdate(BaseModel):
     device_attributes: Optional[Dict[str, Any]] = None
     device_subscription: Optional[Dict[str, Any]] = None
     device_stats: Optional[Dict[str, Any]] = None
+    device_health_settings: Optional[Dict[str, Any]] = None
     events_on: Optional[bool] = None
     device_location_coordinates: Optional[Any] = None  # dict {lat, lng} or legacy str
     device_melodies_all: Optional[List[MelodyMainItem]] = None