fix(module-key): make module keys standalone MD format with system_key relation

backend/app/models/module.py

@@ -1,7 +1,7 @@
 from datetime import datetime
 from uuid import uuid4
 
-from sqlalchemy import DateTime, String, func
+from sqlalchemy import DateTime, ForeignKey, String, func
 from sqlalchemy.dialects.postgresql import UUID
 from sqlalchemy.orm import Mapped, mapped_column
 
@@ -12,6 +12,9 @@ class Module(Base):
     __tablename__ = "modules"
 
     id: Mapped[str] = mapped_column(UUID(as_uuid=False), primary_key=True, default=lambda: str(uuid4()))
+    system_key: Mapped[str] = mapped_column(
+        String(128), ForeignKey("systems.system_key", ondelete="CASCADE"), nullable=False, index=True
+    )
     module_key: Mapped[str] = mapped_column(String(128), unique=True, nullable=False, index=True)
     name: Mapped[str] = mapped_column(String(255), nullable=False)
     status: Mapped[str] = mapped_column(String(16), nullable=False, default="active")