feat(article): expose auto_publish_platforms derived from publish accounts

Replace the freeform `platforms` field on articles/tasks (parsed out of
wizard_state/input_params JSON) with `auto_publish_platforms`, resolved
by joining schedule publish accounts to platform_accounts. The migration
strips the legacy keys from existing rows so the new field is the single
source of truth.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/shared-types/src/index.ts

@@ -557,7 +557,7 @@ export interface ArticleListItem {
   prompt_rule_id: number | null;
   prompt_rule_name: string | null;
   generation_mode: string | null;
-  platforms: string[];
+  auto_publish_platforms: string[];
   generate_status: string;
   publish_status: string;
   title: string | null;
@@ -582,7 +582,7 @@ export interface ArticleDetail {
   template_id: number | null;
   template_name: string | null;
   generation_mode: string | null;
-  platforms: string[];
+  auto_publish_platforms: string[];
   cover_asset_url: string | null;
   cover_image_asset_id: number | null;
   generate_status: string;
@@ -632,7 +632,6 @@ export interface GenerateImitationResponse {
 export interface UpdateArticleRequest {
   title: string;
   markdown_content: string;
-  platforms?: string[];
   cover_asset_url?: string | null;
   referenced_image_asset_ids?: number[];
   cover_image_asset_id?: number | null;
@@ -1448,6 +1447,7 @@ export interface ScheduleTask {
   cron_expr: string;
   auto_publish: boolean;
   publish_account_ids: string[];
+  auto_publish_platforms: string[];
   cover_asset_url: string | null;
   cover_image_asset_id: number | null;
   enable_web_search: boolean;
@@ -1534,7 +1534,7 @@ export interface InstantTaskItem {
   name: string;
   status: string;
   execution_time: string | null;
-  platforms: string[];
+  auto_publish_platforms: string[];
   generate_count: number;
   created_at: string;
 }