Refactor backend: Split models and proxmox_client into modules, add alembic

backend/app/models/base.py

@@ -0,0 +1,16 @@
+from sqlalchemy import Boolean, Column, Integer, BigInteger, String, DateTime, Text, Index, JSON, ForeignKey, Table
+from sqlalchemy.sql import func
+from sqlalchemy.orm import relationship
+from datetime import datetime, timezone
+from typing import Optional
+
+from ..db import Base
+from ..crypto import EncryptedString
+from ..config import utcnow, make_tz_aware
+
+# Just exposing them for the other models to import easily
+__all__ = [
+    'Base', 'EncryptedString', 'utcnow', 'make_tz_aware',
+    'Boolean', 'Column', 'Integer', 'BigInteger', 'String', 'DateTime', 'Text', 'Index', 'JSON', 'ForeignKey', 'Table',
+    'func', 'relationship', 'datetime', 'timezone', 'Optional'
+]