refactor(validation): use ml_id as primary ID, add chembl_id field

src/macro_lactone_toolkit/validation/models.py

@@ -27,7 +27,8 @@ class ParentMolecule(SQLModel, table=True):
     __tablename__ = "parent_molecules"
 
     id: Optional[int] = Field(default=None, primary_key=True)
-    source_id: str = Field(index=True)
+    ml_id: str = Field(index=True)  # MacrolactoneDB unique ID (e.g., ML00000001)
+    chembl_id: Optional[str] = Field(default=None, index=True)  # Original CHEMBL ID
     molecule_name: Optional[str] = None
     smiles: str = Field(index=True)
     classification: str = Field(index=True)