fix(alembic): merge coupon_state + invite 双 head 为单一 head

coupon_state_tables 与 invite_code_and_relation 都挂在 11a1d08c6f55 下、是兄弟迁移,
合 main 后形成两个 head,alembic upgrade head 会报 Multiple head revisions 致部署失败。
本 merge 迁移(无 schema 变更)把两条链并起来,恢复单一 head。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

alembic/versions/0cf18d590b1d_merge_coupon_state_and_invite_heads.py

@@ -0,0 +1,26 @@
+"""merge coupon_state and invite heads
+
+Revision ID: 0cf18d590b1d
+Revises: coupon_state_tables, invite_code_and_relation
+Create Date: 2026-06-08 05:49:29.604571
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = '0cf18d590b1d'
+down_revision: Union[str, Sequence[str], None] = ('coupon_state_tables', 'invite_code_and_relation')
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    pass
+
+
+def downgrade() -> None:
+    pass