修复了一点bug，然后增加了图层拆分更多的功能

database/migrations/0005_seedream_layer_compositions.sql

@@ -0,0 +1,14 @@
+create table if not exists public.seedream_layer_compositions (
+  job_id text primary key references public.generation_jobs(id) on delete cascade,
+  owner_id text not null,
+  base_asset_id text not null,
+  base_visible boolean not null default true,
+  layers jsonb not null default '[]'::jsonb,
+  version bigint not null default 1 check (version > 0),
+  created_at timestamptz not null default now(),
+  updated_at timestamptz not null default now(),
+  constraint seedream_layer_compositions_layers_array_check check (jsonb_typeof(layers) = 'array')
+);
+
+create index if not exists seedream_layer_compositions_owner_updated_idx
+  on public.seedream_layer_compositions(owner_id, updated_at desc);