feat(14-01): add sector CRUD backend with migration, model, service, and router

- Create sectors table migration (034) with RLS and devices.sector_id FK
- Add Sector ORM model with site_id and tenant_id foreign keys
- Add SectorCreate/Update/Response/ListResponse Pydantic schemas
- Implement sector_service with CRUD and device assignment functions
- Add sectors router with GET/POST/PUT/DELETE and device sector assignment
- Register sectors router in main.py
- Add sector_id and sector_name to Device model and DeviceResponse

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

backend/app/models/__init__.py

@@ -14,6 +14,7 @@ from app.models.alert import AlertRule, NotificationChannel, AlertRuleChannel, A
 from app.models.firmware import FirmwareVersion, FirmwareUpgradeJob
 from app.models.config_template import ConfigTemplate, ConfigTemplateTag, TemplatePushJob
 from app.models.site import Site
+from app.models.sector import Sector
 from app.models.audit_log import AuditLog
 from app.models.maintenance_window import MaintenanceWindow
 from app.models.api_key import ApiKey
@@ -32,6 +33,7 @@ __all__ = [
     "DeviceTagAssignment",
     "DeviceStatus",
     "Site",
+    "Sector",
     "AlertRule",
     "NotificationChannel",
     "AlertRuleChannel",

backend/app/models/device.py

@@ -108,6 +108,15 @@ class Device(Base):
         index=True,
     )
     site: Mapped["Site"] = relationship("Site", back_populates="devices")  # type: ignore[name-defined]
+    sector_id: Mapped[uuid.UUID | None] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("sectors.id", ondelete="SET NULL"),
+        nullable=True,
+        index=True,
+    )
+    sector: Mapped["Sector"] = relationship(  # type: ignore[name-defined]
+        "Sector", back_populates="devices", foreign_keys=[sector_id]
+    )
 
     def __repr__(self) -> str:
         return f"<Device id={self.id} hostname={self.hostname!r} tenant_id={self.tenant_id}>"

backend/app/models/sector.py

@@ -0,0 +1,54 @@
+"""Sector model -- directional antenna grouping within a site."""
+
+import uuid
+from datetime import datetime
+
+from sqlalchemy import DateTime, Float, ForeignKey, String, Text, UniqueConstraint, func
+from sqlalchemy.dialects.postgresql import UUID
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.models.base import Base
+
+
+class Sector(Base):
+    __tablename__ = "sectors"
+    __table_args__ = (
+        UniqueConstraint("tenant_id", "site_id", "name", name="uq_sectors_tenant_site_name"),
+    )
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        primary_key=True,
+        default=uuid.uuid4,
+        server_default=func.gen_random_uuid(),
+    )
+    site_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("sites.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    tenant_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("tenants.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    name: Mapped[str] = mapped_column(String(255), nullable=False)
+    azimuth: Mapped[float | None] = mapped_column(Float, nullable=True)
+    description: Mapped[str | None] = mapped_column(Text, nullable=True)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), nullable=False
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), onupdate=func.now(), nullable=False
+    )
+
+    # Relationships
+    site: Mapped["Site"] = relationship("Site")  # type: ignore[name-defined]
+    devices: Mapped[list["Device"]] = relationship(  # type: ignore[name-defined]
+        "Device", back_populates="sector", foreign_keys="[Device.sector_id]"
+    )
+
+    def __repr__(self) -> str:
+        return f"<Sector id={self.id} name={self.name!r} site_id={self.site_id}>"