M39: harden application and acceptance gates

backend/alembic/versions/0a4c1d2e3f5b_idempotency_request_fingerprint.py

@@ -0,0 +1,28 @@
+"""idempotency request fingerprint
+
+Revision ID: 0a4c1d2e3f5b
+Revises: c24f6a9d013e
+Create Date: 2026-08-16 22:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision: str = "0a4c1d2e3f5b"
+down_revision: Union[str, None] = "c24f6a9d013e"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "idempotency_records",
+        sa.Column("request_fingerprint", sa.String(length=64), nullable=True),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("idempotency_records", "request_fingerprint")