US06-03: Preserve Offline Identity and Review Evidence

migrations/versions/0013_protected_thumbnails.py

@@ -0,0 +1,29 @@
+"""Protected thumbnails (US06-03).
+
+Revision ID: 0013_protected_thumbnails
+Revises: 0012_archive_plans
+Create Date: 2026-08-16
+
+A protected thumbnail is the durable comparison preview of an asset whose
+original has left active storage. It is evidence rather than cache, so the LRU
+quota must not evict it: the archive medium may be offline when it is needed.
+"""
+
+import sqlalchemy as sa
+from alembic import op
+
+revision = "0013_protected_thumbnails"
+down_revision = "0012_archive_plans"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "thumbnails",
+        sa.Column("protected", sa.Boolean(), nullable=False, server_default=sa.false()),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("thumbnails", "protected")