重构回忆录为 story-first / markdown-first 架构并整合图片意图与前端 UI 修复

本次 squash merge 将 codex-story-first-image-intent 的整体改动合入 development，核心内容包括：

1. 后端数据与迁移：新增 stories、story_versions、story_image_intents、chapter_cover_intents、assets 等模型与 Alembic 迁移，建立 story-first、markdown-first、asset-first 的主数据链路。

2. 生成与任务链：引入 StoryBuilderOrchestrator、ChapterComposerOrchestrator、story_image_tasks、chapter_cover_tasks，图片生成从正文占位符改为结构化 intent -> asset -> markdown 回填。

3. 并发与一致性：为 story/chapter intent 增加 claim_token、claimed_at、attempt_count，采用数据库原子 claim 为主、Redis 锁为辅，避免重复生成、锁误删和 processing 卡死。

4. Memoir 读写路径：章节 canonical_markdown 成为正文真源，列表/详情接口补齐 markdown、cover_asset、word_count 等字段，PDF 与 asset 解析链路同步升级。

5. Memory / Retrieval：扩展 transcript ingest、chunking、evidence 检索与 story 聚合基础设施，为后续 story-first RAG 与多 agent 编排提供底座。

6. App 端体验：章节页继续走 MarkdownRenderer 阅读链，同时吸收 fix3-19 的跨平台 UI glitch 修复；更新对话页、首页、文案资源与章节列表映射逻辑。

7. 测试与文档：补充 asset resolver、story image task、章节封面派发、markdown 映射等回归测试，并加入图片占位符退役设计文档。

api/tests/test_process_memoir_segments_image_enqueue.py

@@ -15,11 +15,17 @@ def _mock_get_sync_db(db):
 
 
 class ProcessMemoirSegmentsImageEnqueueTest(unittest.TestCase):
-    @patch("app.tasks.memoir_tasks._chapter_has_cover_to_generate", return_value=True)
     @patch(
-        "app.tasks.memoir_tasks._chapter_has_any_section_images_to_generate",
-        return_value=True,
+        "app.features.memory.repo.retrieve_evidence_sync",
+        return_value={
+            "relevant_chunks": [],
+            "relevant_summaries": [],
+            "relevant_facts": [],
+            "timeline_hints": [],
+            "relevant_stories": [],
+        },
     )
+    @patch("app.features.memory.service.ingest_transcript_sync")
     @patch("app.tasks.memoir_tasks._update_task_status_sync")
     @patch("app.tasks.memoir_tasks._release_chapter_lock")
     @patch("app.tasks.memoir_tasks._acquire_chapter_lock", return_value=True)
@@ -30,7 +36,7 @@ class ProcessMemoirSegmentsImageEnqueueTest(unittest.TestCase):
     )
     @patch("app.tasks.memoir_tasks._get_or_create_state_sync")
     @patch("app.tasks.memoir_tasks._get_llm")
-    @patch("app.tasks.memoir_tasks.generate_chapter_images.delay")
+    @patch("app.tasks.chapter_cover_tasks.generate_chapter_cover.delay")
     @patch("app.tasks.memoir_tasks.get_sync_db")
     @patch("app.tasks.memoir_tasks.MemoirImageSettings.from_env")
     def test_process_memoir_segments_parses_markdown_wrapped_state_extraction_json(
@@ -45,8 +51,8 @@ class ProcessMemoirSegmentsImageEnqueueTest(unittest.TestCase):
         _acquire_lock_mock,
         _release_lock_mock,
         _update_status_mock,
-        _has_section_images_mock,
-        _has_cover_mock,
+        ingest_mock,
+        retrieve_mock,
     ):
         settings_from_env.return_value = MemoirImageSettings(
             enabled=True,
@@ -108,15 +114,15 @@ class ProcessMemoirSegmentsImageEnqueueTest(unittest.TestCase):
         empty_sections_result = Mock()
         empty_sections_result.scalars.return_value.all.return_value = []
 
-        cover_check_result = Mock()
-        cover_check_result.scalar_one_or_none.return_value = None
+        version_count_result = Mock()
+        version_count_result.scalar.return_value = 0
 
         db = Mock()
         db.execute.side_effect = [
             segments_result,
             chapter_result,
             empty_sections_result,  # _save_narrative_to_sections 内查询 ChapterSection
-            cover_check_result,  # 封面 MemoirImage 检查
+            version_count_result,  # ensure_chapter_markdown_and_version_sync 内 count
             book_result,
         ]
         db.get.return_value = None
@@ -145,6 +151,17 @@ class ProcessMemoirSegmentsImageEnqueueTest(unittest.TestCase):
         self.assertEqual(len(delay_events), 1)
         self.assertGreater(events.index(delay_events[0]), events.index("commit"))
 
+    @patch(
+        "app.features.memory.repo.retrieve_evidence_sync",
+        return_value={
+            "relevant_chunks": [],
+            "relevant_summaries": [],
+            "relevant_facts": [],
+            "timeline_hints": [],
+            "relevant_stories": [],
+        },
+    )
+    @patch("app.features.memory.service.ingest_transcript_sync")
     @patch("app.tasks.memoir_tasks._update_task_status_sync")
     @patch("app.tasks.memoir_tasks._release_chapter_lock")
     @patch("app.tasks.memoir_tasks._acquire_chapter_lock", return_value=True)
@@ -154,7 +171,7 @@ class ProcessMemoirSegmentsImageEnqueueTest(unittest.TestCase):
     )
     @patch("app.tasks.memoir_tasks._get_or_create_state_sync")
     @patch("app.tasks.memoir_tasks._get_llm", return_value=None)
-    @patch("app.tasks.memoir_tasks.generate_chapter_images.delay")
+    @patch("app.tasks.chapter_cover_tasks.generate_chapter_cover.delay")
     @patch("app.tasks.memoir_tasks.get_sync_db")
     @patch("app.tasks.memoir_tasks.MemoirImageSettings.from_env")
     def test_process_memoir_segments_does_not_enqueue_image_jobs_when_feature_disabled(
@@ -168,6 +185,8 @@ class ProcessMemoirSegmentsImageEnqueueTest(unittest.TestCase):
         _acquire_lock_mock,
         _release_lock_mock,
         _update_status_mock,
+        ingest_mock,
+        retrieve_mock,
     ):
         settings_from_env.return_value = MemoirImageSettings(
             enabled=False,
@@ -203,11 +222,15 @@ class ProcessMemoirSegmentsImageEnqueueTest(unittest.TestCase):
         empty_sections_result = Mock()
         empty_sections_result.scalars.return_value.all.return_value = []
 
+        version_count_result = Mock()
+        version_count_result.scalar.return_value = 0
+
         db = Mock()
         db.execute.side_effect = [
             segments_result,
             chapter_result,
             empty_sections_result,  # _save_narrative_to_sections 内查询 ChapterSection
+            version_count_result,  # ensure_chapter_markdown_and_version_sync 内 count
             book_result,
         ]
         db.get.return_value = None