fix(alembic): merge 双 head(meituan_coupon_image_meta + 4dc2af7ebe74)

#71 的 meituan_coupon_image_meta 与并行合入的 4dc2af7ebe74(device_65/comparison_token 合并)
形成两个 alembic head,`alembic upgrade head` 报 "Multiple head revisions"。加一个空 merge 迁移
把两 head 合一,恢复 upgrade head 单 head 可用(线上已临时用 upgrade heads 应用两条)。

alembic/versions/merge_heads_image_meta_20260623_merge_meituan_coupon_image_meta_.py

@@ -0,0 +1,26 @@
+"""merge meituan_coupon_image_meta + 4dc2af7ebe74(device/comparison) heads
+
+Revision ID: merge_heads_image_meta_20260623
+Revises: 4dc2af7ebe74, meituan_coupon_image_meta
+Create Date: 2026-06-23 21:32:11.888579
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = 'merge_heads_image_meta_20260623'
+down_revision: Union[str, Sequence[str], None] = ('4dc2af7ebe74', 'meituan_coupon_image_meta')
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    pass
+
+
+def downgrade() -> None:
+    pass