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/migrations/20260401180001_create_schedule_tasks.up.sql

@@ -5,7 +5,6 @@ CREATE TABLE schedule_tasks (
     brand_id        BIGINT REFERENCES brands(id),
     name            VARCHAR(100) NOT NULL,
     cron_expr       VARCHAR(100) NOT NULL,
-    target_platform VARCHAR(50),
     start_at        TIMESTAMPTZ,
     end_at          TIMESTAMPTZ,
     next_run_at     TIMESTAMPTZ,

server/migrations/20260413120000_enhance_schedule_tasks.down.sql

@@ -7,10 +7,3 @@ ALTER TABLE schedule_tasks
     DROP COLUMN IF EXISTS generate_count,
     DROP COLUMN IF EXISTS enable_web_search,
     DROP COLUMN IF EXISTS operator_id;
-
-ALTER TABLE schedule_tasks
-    ALTER COLUMN target_platform TYPE VARCHAR(50)
-    USING CASE
-        WHEN target_platform IS NULL THEN NULL
-        ELSE LEFT(target_platform, 50)
-    END;

server/migrations/20260413120000_enhance_schedule_tasks.up.sql

@@ -1,6 +1,3 @@
-ALTER TABLE schedule_tasks
-    ALTER COLUMN target_platform TYPE TEXT;
-
 ALTER TABLE schedule_tasks
     ADD COLUMN operator_id BIGINT REFERENCES users(id),
     ADD COLUMN enable_web_search BOOLEAN NOT NULL DEFAULT FALSE,

server/migrations/20260430120000_add_schedule_auto_publish.down.sql

@@ -0,0 +1,11 @@
+DROP INDEX IF EXISTS idx_schedule_task_workspace;
+
+ALTER TABLE schedule_tasks
+    DROP CONSTRAINT IF EXISTS chk_schedule_tasks_publish_account_ids_json;
+
+ALTER TABLE schedule_tasks
+    DROP COLUMN IF EXISTS cover_image_asset_id,
+    DROP COLUMN IF EXISTS cover_asset_url,
+    DROP COLUMN IF EXISTS publish_account_ids,
+    DROP COLUMN IF EXISTS auto_publish,
+    DROP COLUMN IF EXISTS workspace_id;

server/migrations/20260430120000_add_schedule_auto_publish.up.sql

@@ -0,0 +1,14 @@
+ALTER TABLE schedule_tasks
+    ADD COLUMN workspace_id BIGINT REFERENCES workspaces(id),
+    ADD COLUMN auto_publish BOOLEAN NOT NULL DEFAULT FALSE,
+    ADD COLUMN publish_account_ids JSONB NOT NULL DEFAULT '[]'::jsonb,
+    ADD COLUMN cover_asset_url TEXT,
+    ADD COLUMN cover_image_asset_id BIGINT;
+
+ALTER TABLE schedule_tasks
+    ADD CONSTRAINT chk_schedule_tasks_publish_account_ids_json
+        CHECK (jsonb_typeof(publish_account_ids) = 'array');
+
+CREATE INDEX idx_schedule_task_workspace
+    ON schedule_tasks(tenant_id, workspace_id, created_at DESC)
+    WHERE deleted_at IS NULL;