fix(watcher): getDifference needs a date, and only a completed drain counts

backend/migrations/versions/a7f3d2b81c04_retry_bot_backlog.py

@@ -0,0 +1,25 @@
+"""retry bot backlog
+
+Revision ID: a7f3d2b81c04
+Revises: e2c9a41f7b68
+Create Date: 2026-09-18 17:30:00.000000
+
+"""
+
+from collections.abc import Sequence
+
+from alembic import op
+
+revision: str = "a7f3d2b81c04"
+down_revision: str | None = "e2c9a41f7b68"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def upgrade() -> None:
+    """No drain has succeeded yet, so let every bot try the queue once more."""
+    op.execute("UPDATE watched_bots SET backfilled_at = NULL")
+
+
+def downgrade() -> None:
+    pass