feat: 完成 SKU 图片选择及素材导入后端

packages/database/migrations/031_sku_image_limit.sql

@@ -0,0 +1,8 @@
+SET search_path TO atlas, public;
+
+-- SKU 图片上限扩展到 30 张，保持与编辑草稿契约一致。
+ALTER TABLE product_variant_listing_media
+    DROP CONSTRAINT product_variant_listing_media_sort_order_check;
+ALTER TABLE product_variant_listing_media
+    ADD CONSTRAINT product_variant_listing_media_sort_order_check
+    CHECK (sort_order >= 0 AND sort_order < 30);

packages/database/migrations/032_product_image_imports.sql

@@ -0,0 +1,21 @@
+SET search_path TO atlas, public;
+
+-- 网络图片导入记录与正式素材分开，保留来源 URL 供候选区回显。
+CREATE TABLE product_image_imports (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    workspace_id UUID NOT NULL REFERENCES workspaces(id) ON DELETE RESTRICT,
+    source_url TEXT NOT NULL,
+    asset_id UUID NOT NULL,
+    created_by_user_id UUID REFERENCES users(id) ON DELETE SET NULL,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+    FOREIGN KEY (workspace_id, asset_id) REFERENCES media_assets(workspace_id, id) ON DELETE RESTRICT,
+    UNIQUE (workspace_id, source_url)
+);
+CREATE INDEX ix_product_image_imports_recent
+    ON product_image_imports (workspace_id, updated_at DESC, id DESC);
+ALTER TABLE product_image_imports ENABLE ROW LEVEL SECURITY;
+ALTER TABLE product_image_imports FORCE ROW LEVEL SECURITY;
+CREATE POLICY workspace_isolation ON product_image_imports
+    USING (workspace_id = app_current_workspace_id())
+    WITH CHECK (workspace_id = app_current_workspace_id());