第11环裂变重写：对齐上线版 split.js 一次LLM出N套完整笔记包

架构从"扇出N个GenerationTask各跑完整管道"改为"一次LLM调用直接出N套
完整笔记包(N=1~5)"，落 FissionNote 表 + 独立展示页。

后端：
- 018迁移：fission_notes 表(文案JSON+score+passed+imagePlan+images+status)
- fission_prompt：FISSION_SYSTEM+三档参考度(low/mid/high)+normalize_tags+品类兜底
- fission_pipeline：一次LLM出N套→各评分(@80合格线)→排序→落库,不达标标
  needs_optimization 非丢弃；apiports 503 回落 codeproxy gpt-5.5 强档兜底
- fission_images：每套串行调现有生图接口(零改动image_gen/storyboard)
- tasks.py：run_fission_pipeline Celery task，删旧扇出注入
- api/v1/fission：进度聚合FissionNote + GET /fission/{id}/notes(剥内部字段)

前端：FissionProgress对齐状态机 + N套独立展示页 + FissionNoteCard

测试：test_fission_engine(19)+test_fission_pipeline(5) 全过；104 全量回归绿

实测task5(fanout=2,mid)端到端跑通：一次出2套→seq0=85过/seq1=79标优化→
生图codeproxy/edits→1024×1536去AI化→task completed→notes端点返完整数据

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/app/services/fission_images.py

@@ -0,0 +1,81 @@
+"""
+app/services/fission_images.py — 第11环裂变 逐套生图（从 fission_pipeline 拆出）
+
+复用单篇 generate_storyboard_images（codeproxy edits 带产品参考图），结果存
+FissionNote.images_json。拆分原因：fission_pipeline.py 超 200 行红线上限。
+🔴 生图引擎零改动；串行跑各套（套内 storyboard 已 asyncio.gather 并发）避免打爆中转站。
+"""
+import logging
+
+from sqlalchemy.orm import Session
+
+logger = logging.getLogger(__name__)
+
+
+def generate_fission_images(
+    db: Session, clients, ft, product: dict, image_count: int, note_ids: list[int],
+) -> None:
+    """逐套生图，结果存 FissionNote.images_json。
+
+    每套用该套自己的 note_json（含定制 imagePlan）当 note 喂生图引擎。
+    产品参考图沿用源产品同一张，与单篇一致。
+    """
+    import asyncio
+    import json as _json
+    import os
+
+    from app.models.fission import FissionNote
+    from app.core.config import get_settings
+    from app.services.ai_engine.image_gen import generate_storyboard_images
+    from app.services.ai_engine.image_postprocessor import process_image
+    from app.workers.pipeline_io import _resolve_image_path
+
+    reference_images = None
+    _img_path = _resolve_image_path(product.get("image_path", ""))
+    if _img_path and os.path.isfile(_img_path):
+        try:
+            with open(_img_path, "rb") as f:
+                reference_images = [f.read()]
+        except Exception as e:  # noqa: BLE001
+            logger.warning("裂变参考图读取失败，无参考图模式: %s", e)
+
+    upload_base = get_settings().UPLOAD_ABS_ROOT
+    for nid in note_ids:
+        fn = db.query(FissionNote).filter(FissionNote.id == nid).first()
+        if not fn:
+            continue
+        try:
+            note = _json.loads(fn.note_json) if fn.note_json else {}
+        except (ValueError, TypeError):
+            note = {}
+        try:
+            results = asyncio.run(generate_storyboard_images(
+                client=clients, note=note, product=product,
+                image_count=image_count, reference_images=reference_images,
+            ))
+        except Exception as exc:  # noqa: BLE001
+            logger.error("裂变套 seq=%s 生图失败: %s", fn.seq, exc)
+            fn.status = "failed"; db.commit()
+            continue
+
+        img_dir = os.path.join(upload_base, str(ft.workspace_id), f"fission_{ft.id}", str(fn.seq))
+        os.makedirs(img_dir, exist_ok=True)
+        images: list[dict] = []
+        for i, r in enumerate(results):
+            if r.get("error") or not r.get("image_bytes"):
+                images.append({"role": r.get("role", ""), "error": str(r.get("error", "生图失败"))[:64]})
+                continue
+            try:
+                processed = process_image(r["image_bytes"], aspect_ratio="3:4", resample_strength=1)
+            except Exception:  # noqa: BLE001
+                processed = r["image_bytes"]
+            fname = f"{i + 1:02d}_{r['role']}.jpg"
+            with open(os.path.join(img_dir, fname), "wb") as f:
+                f.write(processed)
+            images.append({
+                "role": r["role"], "seq": i + 1,
+                "url": f"/uploads/{ft.workspace_id}/fission_{ft.id}/{fn.seq}/{fname}",
+            })
+        fn.images_json = _json.dumps(images, ensure_ascii=False)
+        fn.status = "image_done"
+        db.commit()