feat(15-01): add site alert rules/events migration, models, schemas, and config

- Create Alembic migration 035 with site_alert_rules and site_alert_events tables, RLS policies, and GRANT
- Add SiteAlertRule/SiteAlertEvent ORM models with enums for rule_type, severity, state
- Add Pydantic schemas for rule/event CRUD and signal history points
- Add SIGNAL_DEGRADATION_THRESHOLD_DB, ALERT_EVALUATION_INTERVAL_SECONDS, TREND_DETECTION_INTERVAL_SECONDS to Settings

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/schemas/site_alert.py

@@ -0,0 +1,168 @@
+"""Pydantic schemas for site alert rules, events, and signal history."""
+
+import uuid
+from datetime import datetime
+from typing import Optional
+
+from pydantic import BaseModel, ConfigDict, field_validator
+
+
+class SiteAlertRuleCreate(BaseModel):
+    """Schema for creating a new site alert rule."""
+
+    name: str
+    rule_type: str
+    threshold_value: float
+    threshold_unit: str
+    sector_id: Optional[uuid.UUID] = None
+    description: Optional[str] = None
+    enabled: bool = True
+
+    @field_validator("name")
+    @classmethod
+    def validate_name(cls, v: str) -> str:
+        v = v.strip()
+        if len(v) < 1 or len(v) > 255:
+            raise ValueError("Rule name must be 1-255 characters")
+        return v
+
+    @field_validator("rule_type")
+    @classmethod
+    def validate_rule_type(cls, v: str) -> str:
+        allowed = {
+            "device_offline_percent",
+            "device_offline_count",
+            "sector_signal_avg",
+            "sector_client_drop",
+            "signal_degradation",
+        }
+        if v not in allowed:
+            raise ValueError(f"rule_type must be one of: {', '.join(sorted(allowed))}")
+        return v
+
+    @field_validator("threshold_unit")
+    @classmethod
+    def validate_threshold_unit(cls, v: str) -> str:
+        allowed = {"percent", "count", "dBm"}
+        if v not in allowed:
+            raise ValueError(f"threshold_unit must be one of: {', '.join(sorted(allowed))}")
+        return v
+
+
+class SiteAlertRuleUpdate(BaseModel):
+    """Schema for updating an existing site alert rule. All fields optional."""
+
+    name: Optional[str] = None
+    rule_type: Optional[str] = None
+    threshold_value: Optional[float] = None
+    threshold_unit: Optional[str] = None
+    sector_id: Optional[uuid.UUID] = None
+    description: Optional[str] = None
+    enabled: Optional[bool] = None
+
+    @field_validator("name")
+    @classmethod
+    def validate_name(cls, v: Optional[str]) -> Optional[str]:
+        if v is None:
+            return v
+        v = v.strip()
+        if len(v) < 1 or len(v) > 255:
+            raise ValueError("Rule name must be 1-255 characters")
+        return v
+
+    @field_validator("rule_type")
+    @classmethod
+    def validate_rule_type(cls, v: Optional[str]) -> Optional[str]:
+        if v is None:
+            return v
+        allowed = {
+            "device_offline_percent",
+            "device_offline_count",
+            "sector_signal_avg",
+            "sector_client_drop",
+            "signal_degradation",
+        }
+        if v not in allowed:
+            raise ValueError(f"rule_type must be one of: {', '.join(sorted(allowed))}")
+        return v
+
+    @field_validator("threshold_unit")
+    @classmethod
+    def validate_threshold_unit(cls, v: Optional[str]) -> Optional[str]:
+        if v is None:
+            return v
+        allowed = {"percent", "count", "dBm"}
+        if v not in allowed:
+            raise ValueError(f"threshold_unit must be one of: {', '.join(sorted(allowed))}")
+        return v
+
+
+class SiteAlertRuleResponse(BaseModel):
+    """Site alert rule response schema."""
+
+    id: uuid.UUID
+    tenant_id: uuid.UUID
+    site_id: uuid.UUID
+    sector_id: Optional[uuid.UUID] = None
+    rule_type: str
+    name: str
+    description: Optional[str] = None
+    threshold_value: float
+    threshold_unit: str
+    enabled: bool
+    created_at: datetime
+    updated_at: datetime
+
+    model_config = ConfigDict(from_attributes=True)
+
+
+class SiteAlertRuleListResponse(BaseModel):
+    """List of site alert rules with total count."""
+
+    items: list[SiteAlertRuleResponse]
+    total: int
+
+
+class SiteAlertEventResponse(BaseModel):
+    """Site alert event response schema."""
+
+    id: uuid.UUID
+    tenant_id: uuid.UUID
+    site_id: uuid.UUID
+    sector_id: Optional[uuid.UUID] = None
+    rule_id: Optional[uuid.UUID] = None
+    device_id: Optional[uuid.UUID] = None
+    link_id: Optional[uuid.UUID] = None
+    severity: str
+    message: str
+    state: str
+    consecutive_hits: int
+    triggered_at: datetime
+    resolved_at: Optional[datetime] = None
+    resolved_by: Optional[uuid.UUID] = None
+
+    model_config = ConfigDict(from_attributes=True)
+
+
+class SiteAlertEventListResponse(BaseModel):
+    """List of site alert events with total count."""
+
+    items: list[SiteAlertEventResponse]
+    total: int
+
+
+class SignalHistoryPoint(BaseModel):
+    """A single time-bucketed signal history data point."""
+
+    timestamp: datetime
+    signal_avg: int
+    signal_min: int
+    signal_max: int
+
+
+class SignalHistoryResponse(BaseModel):
+    """Signal history response with time-bucketed data points."""
+
+    items: list[SignalHistoryPoint]
+    mac_address: str
+    range: str