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>

server/internal/tenant/app/instant_task_service.go

@@ -31,16 +31,16 @@ type InstantTaskListParams struct {
 }
 
 type InstantTaskResponse struct {
-	ID             int64    `json:"id"`
-	ArticleID      *int64   `json:"article_id"`
-	PromptRuleID   *int64   `json:"prompt_rule_id"`
-	PromptRuleName *string  `json:"prompt_rule_name"`
-	Name           string   `json:"name"`
-	Status         string   `json:"status"`
-	ExecutionTime  *string  `json:"execution_time"`
-	Platforms      []string `json:"platforms"`
-	GenerateCount  int      `json:"generate_count"`
-	CreatedAt      string   `json:"created_at"`
+	ID                   int64    `json:"id"`
+	ArticleID            *int64   `json:"article_id"`
+	PromptRuleID         *int64   `json:"prompt_rule_id"`
+	PromptRuleName       *string  `json:"prompt_rule_name"`
+	Name                 string   `json:"name"`
+	Status               string   `json:"status"`
+	ExecutionTime        *string  `json:"execution_time"`
+	AutoPublishPlatforms []string `json:"auto_publish_platforms"`
+	GenerateCount        int      `json:"generate_count"`
+	CreatedAt            string   `json:"created_at"`
 }
 
 type InstantTaskListResponse struct {
@@ -123,7 +123,11 @@ func (s *InstantTaskService) List(ctx context.Context, params InstantTaskListPar
 
 		item.ExecutionTime = stringPtrFromDBValue(executionAt)
 		item.CreatedAt = fmt.Sprintf("%v", createdAt)
-		item.Platforms = resolveArticlePlatforms(nil, inputParamsJSON)
+		autoPublishPlatforms, err := loadScheduleAutoPublishPlatforms(ctx, s.pool, actor.TenantID, inputParamsJSON)
+		if err != nil {
+			return nil, response.ErrInternal(50010, "query_failed", "failed to resolve instant task auto publish platforms")
+		}
+		item.AutoPublishPlatforms = autoPublishPlatforms
 		item.GenerateCount = 1
 
 		if len(inputParamsJSON) > 0 {