feat(api): 拆分章节物化与 Story 后处理，并加固 Redis 锁与腾讯 ASR

回忆录 Story 流水线（同步）
- 同步路径仅写入 Story 与章节关联，改为 mark_chapter_dirty_sync，不再内联 compose
- 物化由 Celery recompose_chapter 异步完成；compose 不变量与异常时保留 dirty 的语义在 repo 中补充说明
- Evidence：大批次时降低 top_k；路由候选 story 携带 char_count/version_count；append 超长/版本过多时强制新开 story
- 叙事 prompt：relevant_chunks 去重，减少重复证据噪声
- 叙事回退与忠实度 gate：返回 fallback 类型并记录结构化日志（含耗时、JSON 有效性等）

Post-commit 与任务编排
- 新增 post_commit.enqueue_story_post_commit_effects：统一派发 generate_story_image（Redis 去重）、延迟 recompose_chapter、可选 memory compaction
- memoir_tasks / story_service / story_image_tasks 改为调用 post-commit 入口；主图回填后按关联章节重算并调度物化与 compacs（锁委托、Redis 单例、ASR to_thread）
- 更新 test_narrative_pipeline 以适配 _apply_narrative_fallbacks 返回值

api/app/features/story/service.py

@@ -11,11 +11,10 @@ from datetime import datetime, timezone
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.core.logging import get_logger
-from app.features.memoir.asset_resolver import strip_asset_image_refs_from_markdown
 from app.features.memoir import repo as memoir_repo
+from app.features.memoir.asset_resolver import strip_asset_image_refs_from_markdown
 from app.features.memoir.memoir_images.settings import MemoirImageSettings
 from app.features.story.image_intent_extractor import extract_primary_image_intent
-from app.features.story.time_hints import apply_infer_story_time_start_to_model
 from app.features.story.repo import (
     count_story_versions,
     create_story,
@@ -27,6 +26,7 @@ from app.features.story.repo import (
     get_story_by_id,
     get_story_image_intent_by_story,
 )
+from app.features.story.time_hints import apply_infer_story_time_start_to_model
 
 logger = get_logger(__name__)
 
@@ -156,17 +156,26 @@ class StoryService:
             await memoir_repo.mark_chapters_dirty_for_story(self._db, story.id)
         await self._db.commit()
         if md.strip():
-            from app.tasks.chapter_compose_tasks import recompose_chapters_for_story
-            from app.tasks.story_image_tasks import generate_story_image
+            from app.features.memoir.repo import get_chapter_ids_linked_to_story
+            from app.features.story.post_commit import enqueue_story_post_commit_effects
 
-            try:
-                generate_story_image.delay(story.id)
-            except Exception as exc:
-                logger.warning("派发 generate_story_image 失败: {}", exc)
-            try:
-                recompose_chapters_for_story.delay(story.id)
-            except Exception as exc:
-                logger.warning("派发 recompose_chapters_for_story 失败: {}", exc)
+            chapter_ids = set(await get_chapter_ids_linked_to_story(self._db, story.id))
+            pc = enqueue_story_post_commit_effects(
+                user_id=user_id,
+                story_ids={story.id},
+                chapter_ids=chapter_ids,
+                trigger_source="manual_api",
+                need_compaction=False,
+            )
+            logger.info(
+                "event=story_post_commit user_id={} trigger=manual_api "
+                "enqueued_story_image_count={} enqueued_chapter_recompose_count={} "
+                "errors={}",
+                user_id,
+                pc.enqueued_story_image_count,
+                pc.enqueued_chapter_recompose_count,
+                pc.errors,
+            )
         return story.id
 
     async def append_version(
@@ -208,17 +217,25 @@ class StoryService:
         )
         await memoir_repo.mark_chapters_dirty_for_story(self._db, story_id)
         await self._db.commit()
-        from app.tasks.chapter_compose_tasks import recompose_chapters_for_story
-        from app.tasks.story_image_tasks import generate_story_image
+        from app.features.memoir.repo import get_chapter_ids_linked_to_story
+        from app.features.story.post_commit import enqueue_story_post_commit_effects
 
-        try:
-            generate_story_image.delay(story_id)
-        except Exception as exc:
-            logger.warning("派发 generate_story_image 失败: {}", exc)
-        try:
-            recompose_chapters_for_story.delay(story_id)
-        except Exception as exc:
-            logger.warning("派发 recompose_chapters_for_story 失败: {}", exc)
+        chapter_ids = set(await get_chapter_ids_linked_to_story(self._db, story_id))
+        pc = enqueue_story_post_commit_effects(
+            user_id=story.user_id,
+            story_ids={story_id},
+            chapter_ids=chapter_ids,
+            trigger_source="manual_api",
+            need_compaction=False,
+        )
+        logger.info(
+            "event=story_post_commit user_id={} trigger=manual_api_append "
+            "enqueued_story_image_count={} enqueued_chapter_recompose_count={} errors={}",
+            story.user_id,
+            pc.enqueued_story_image_count,
+            pc.enqueued_chapter_recompose_count,
+            pc.errors,
+        )
         return version.id
 
     async def link_evidence(