A: Add Address model — polymorphic multi-address support

app/models/address.py

@@ -0,0 +1,52 @@
+"""Address model — polymorphic addresses for companies and contacts."""
+
+from __future__ import annotations
+
+import uuid
+
+from sqlalchemy import Boolean, Index, String, UniqueConstraint
+from sqlalchemy.dialects.postgresql import UUID as PGUUID
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.core.db import Base, TenantMixin
+
+
+class Address(Base, TenantMixin):
+    """Polymorphic address entity — multiple addresses per company or contact.
+
+    entity_type: 'company' or 'contact'
+    entity_id: FK to companies.id or contacts.id
+    address_type: billing, shipping, headquarters, branch, private, other
+    is_default: one default address per (entity_type, entity_id, address_type)
+    """
+
+    __tablename__ = "addresses"
+    __table_args__ = (
+        UniqueConstraint(
+            "tenant_id",
+            "entity_type",
+            "entity_id",
+            "address_type",
+            "is_default",
+            name="uq_address_default_per_type",
+        ),
+        Index("ix_addresses_tenant_entity", "tenant_id", "entity_type", "entity_id"),
+        Index("ix_addresses_tenant_type", "tenant_id", "address_type"),
+    )
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        PGUUID(as_uuid=True), primary_key=True, default=uuid.uuid4
+    )
+    entity_type: Mapped[str] = mapped_column(String(50), nullable=False)
+    entity_id: Mapped[uuid.UUID] = mapped_column(
+        PGUUID(as_uuid=True), nullable=False, index=True
+    )
+    label: Mapped[str] = mapped_column(String(100), nullable=False)
+    address_type: Mapped[str] = mapped_column(String(50), nullable=False)
+    street: Mapped[str | None] = mapped_column(String(255), nullable=True)
+    street_number: Mapped[str | None] = mapped_column(String(20), nullable=True)
+    city: Mapped[str | None] = mapped_column(String(100), nullable=True)
+    zip: Mapped[str | None] = mapped_column(String(20), nullable=True)
+    state: Mapped[str | None] = mapped_column(String(100), nullable=True)
+    country: Mapped[str | None] = mapped_column(String(2), nullable=True)
+    is_default: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)