feat: move unified generation to background worker

backend/app/services/generation_jobs.py

@@ -6,7 +6,7 @@ from datetime import datetime, timedelta, timezone
 from typing import Any
 
 from fastapi import HTTPException
-from sqlalchemy import desc, select
+from sqlalchemy import desc, select, update
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.core.config import settings
@@ -59,6 +59,7 @@ def _job_progress(job: GenerationJob) -> dict[str, Any]:
 
     progress_map: dict[str, tuple[int, str]] = {
         "request_accepted": (5, "已接收请求"),
+        "worker_started": (12, "后台任务已开始"),
         "context_prepared": (20, "上下文已准备"),
         "narrative_generated": (45, "正文已生成"),
         "story_saved": (60, "主记录已保存"),
@@ -66,8 +67,18 @@ def _job_progress(job: GenerationJob) -> dict[str, Any]:
         "provider_call_succeeded": (72, "Provider 调用成功"),
         "provider_call_failed": (72, "Provider 调用失败，尝试恢复"),
         "cover_image_started": (75, "封面生成中"),
+        "cover_image_succeeded": (88, "封面已生成"),
+        "cover_image_failed": (88, "封面生成失败"),
         "storybook_images_started": (75, "绘本插图生成中"),
+        "storybook_cover_image_succeeded": (82, "绘本封面已生成"),
+        "storybook_cover_image_failed": (82, "绘本封面生成失败"),
+        "storybook_page_image_succeeded": (86, "分页插图已生成"),
+        "storybook_page_image_failed": (86, "分页插图生成失败"),
+        "storybook_images_completed": (92, "绘本插图已完成"),
         "audio_started": (75, "音频生成中"),
+        "audio_cache_hit": (88, "音频缓存已复用"),
+        "audio_succeeded": (88, "音频已生成"),
+        "audio_failed": (88, "音频生成失败"),
         "asset_retry_started": (25, "资源重试中"),
         "postprocessing_queued": (90, "后处理已排队"),
         "asset_generation_completed": (100, "资源已完成"),
@@ -155,6 +166,10 @@ async def record_generation_event(
 ) -> GenerationJobEvent:
     """Append one event to an existing generation job."""
 
+    job.current_step = event_type
+    if story_id is not None:
+        job.story_id = story_id
+
     event = GenerationJobEvent(
         job_id=job.id,
         story_id=story_id if story_id is not None else job.story_id,
@@ -169,6 +184,42 @@ async def record_generation_event(
     return event
 
 
+async def claim_generation_job_for_worker(
+    db: AsyncSession,
+    *,
+    job_id: str,
+) -> GenerationJob | None:
+    """Claim one queued generation job for worker execution once."""
+
+    claim_result = await db.execute(
+        update(GenerationJob)
+        .where(
+            GenerationJob.id == job_id,
+            GenerationJob.status == "running",
+            GenerationJob.current_step == "request_accepted",
+        )
+        .values(current_step="worker_started")
+    )
+    await db.commit()
+
+    if not claim_result.rowcount:
+        return None
+
+    result = await db.execute(select(GenerationJob).where(GenerationJob.id == job_id))
+    job = result.scalar_one_or_none()
+    if job is None:
+        return None
+
+    await record_generation_event(
+        db,
+        job=job,
+        event_type="worker_started",
+        status="running",
+        message="Generation worker started processing the accepted request.",
+    )
+    return job
+
+
 async def finish_generation_job(
     db: AsyncSession,
     *,