softdelete users and migration script

backend/app/models.py

@@ -84,13 +84,24 @@ class RadadminClient(Base):
     __tablename__ = "radadmin_clients"
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
-    mac_address: Mapped[str] = mapped_column(String(17), nullable=False, unique=True)
+    # Not DB-unique on its own — uniqueness is enforced only among live rows by the
+    # generated `active_mac` column (see radadmin_schema.sql). Soft-deleted rows
+    # (deleted_at set) may share a mac_address with the live row and each other.
+    mac_address: Mapped[str] = mapped_column(String(17), nullable=False)
     name: Mapped[str | None] = mapped_column(String(128), nullable=True)
     phone: Mapped[str | None] = mapped_column(String(32), nullable=True)
     alias: Mapped[str | None] = mapped_column(String(64), nullable=True)
+    # Mirror of the client's group (radusergroup) and billing status (customers):
+    # set on add, synced on edit, and kept frozen on the row after soft-delete so
+    # the deleted client's group/status survive their hard-deleted source rows.
+    groupname: Mapped[str | None] = mapped_column(String(64), nullable=True, default=None)
+    status: Mapped[str | None] = mapped_column(String(10), nullable=True, default=None)
     created_at: Mapped[datetime | None] = mapped_column(
         DateTime, nullable=True, server_default=func.current_timestamp()
     )
+    # Soft delete: NULL = live, a timestamp = deleted. Deleted rows are never
+    # returned by the API and are kept only for restore/reference.
+    deleted_at: Mapped[datetime | None] = mapped_column(DateTime, nullable=True, default=None)
 
 
 class RadadminDevice(Base):