feat: add mail import detail events

backend/alembic/versions/f6a7b8c9d0e1_add_mail_source_import_details.py

@@ -0,0 +1,27 @@
+"""add mail source import details
+
+Revision ID: f6a7b8c9d0e1
+Revises: e5f6a7b8c9d0
+Create Date: 2026-05-22 20:05:00.000000
+
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "f6a7b8c9d0e1"
+down_revision: Union[str, Sequence[str], None] = "e5f6a7b8c9d0"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Add a sanitized details payload to import history rows."""
+    op.add_column("mail_source_imports", sa.Column("details", sa.Text(), nullable=True))
+
+
+def downgrade() -> None:
+    """Remove import details payloads."""
+    op.drop_column("mail_source_imports", "details")