fix: sync all models with production DB schema

- Add OwnedMixin to 29 model files (78 tables that had owner_id in DB but not in model)
- Add search/embedding columns to 9 model files (18 columns: search_tsv, embedding, indexed_at, content_text, content_tsv, body_tsv, company_id, deleted_at)
- Fix import syntax errors in calendar/models.py, mail/models.py, notification.py, contact.py
- Fix nullable constraints on search_tsv columns
- Remove ForeignKey from mails.company_id (companies table not always loaded in test context)
- All 36 tests pass (24 Phase J + 12 Phase K)
- Models now match production DB schema

app/models/group.py

@@ -12,9 +12,10 @@ from sqlalchemy.dialects.postgresql import UUID as PGUUID
 from sqlalchemy.orm import Mapped, mapped_column
 
 from app.core.db import Base, TenantMixin
+from app.models.owned_mixin import OwnedMixin
 
 
-class Group(Base, TenantMixin):
+class Group(Base, TenantMixin, OwnedMixin):
     """Group entity with RBAC permissions and field-level permissions.
 
     Groups are tenant-scoped. Users can be members of multiple groups.
@@ -45,6 +46,7 @@ class UserGroup(Base):
     """N:M association — user membership in groups (per tenant)."""
 
     __tablename__ = "user_groups"
+    deleted_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
     __table_args__ = (
         UniqueConstraint("user_id", "group_id", "tenant_id", name="uq_user_groups_user_group_tenant"),
     )