1、后台界面/video-engines，添加修改需要增加可传图片和视频的数量

2、前台接口/credits/ratios，同步返回

video-gen-api/alembic/versions/f7a3b2c1d4e5_add_max_image_video_count.py

@@ -0,0 +1,27 @@
+"""add max image and video count to video engines
+
+Revision ID: f7a3b2c1d4e5
+Revises: e5f260ed1459
+Create Date: 2026-07-01 00:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+revision: str = 'f7a3b2c1d4e5'
+down_revision: Union[str, None] = 'e5f260ed1459'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column('video_engines', sa.Column('max_image_count', sa.Integer(), server_default='5', nullable=False))
+    op.add_column('video_engines', sa.Column('max_video_count', sa.Integer(), server_default='2', nullable=False))
+
+
+def downgrade() -> None:
+    op.drop_column('video_engines', 'max_video_count')
+    op.drop_column('video_engines', 'max_image_count')