feat(schedule-tasks): support auto-publish via media accounts

Replace the legacy target_platform string on schedule tasks with a
workspace-aware auto-publish payload (auto_publish + publish_account_ids
JSONB + cover_asset_url + cover_image_asset_id) and migrate the schema,
sqlc queries, generated models, domain struct, ScheduleTaskService DTOs,
and dispatch worker to round-trip the new fields. PromptRuleGeneration
gains a WithPublishJobService hook so executeGeneration can enqueue an
auto-publish job once the article is ready, and worker-generate wires
the publish-job service in. On the admin-web side, extract
PublishArticleModal's account-card builders into a shared
publish-account-cards module, rebuild GenerateTaskDrawer's schedule
mode around account selection plus a CoverPickerModal, and surface the
new "auto publish" column on ScheduleTaskTab. Shared types and i18n
strings cover the new fields.

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

server/internal/tenant/domain/schedule_task.go

@@ -3,20 +3,24 @@ package domain
 import "time"
 
 type ScheduleTask struct {
-	ID              int64
-	TenantID        int64
-	OperatorID      *int64
-	PromptRuleID    int64
-	BrandID         *int64
-	Name            string
-	CronExpr        string
-	TargetPlatform  *string
-	EnableWebSearch bool
-	GenerateCount   int
-	StartAt         *time.Time
-	EndAt           *time.Time
-	NextRunAt       *time.Time
-	Status          string
-	CreatedAt       time.Time
-	UpdatedAt       time.Time
+	ID                int64
+	TenantID          int64
+	WorkspaceID       *int64
+	OperatorID        *int64
+	PromptRuleID      int64
+	BrandID           *int64
+	Name              string
+	CronExpr          string
+	AutoPublish       bool
+	PublishAccountIDs []string
+	CoverAssetURL     *string
+	CoverImageAssetID *int64
+	EnableWebSearch   bool
+	GenerateCount     int
+	StartAt           *time.Time
+	EndAt             *time.Time
+	NextRunAt         *time.Time
+	Status            string
+	CreatedAt         time.Time
+	UpdatedAt         time.Time
 }