feat(api+app): 对话阶段化、回忆录流水线与客户端会话体验

- DB: segments 用户输入文本（Alembic 0002）
- Chat: 阶段检测/阶段提示/回复限制，编排与访谈/画像 prompts 调整
- Memoir: 忠实度检查 agent，叙事与分类等链路更新
- Core: agent 日志、Alembic 启动、LangChain/日志/配置等
- Story: time_hints；Memory 检索与相关测试
- Expo: 助手头像、会话页与消息拆分、实时会话与文案/i18n
- Docs/scripts/tests: 迁移脚本、LLM JSON/记忆检索文档、新增单测

api/app/features/story/service.py

@@ -15,6 +15,7 @@ from app.features.memoir.asset_resolver import strip_asset_image_refs_from_markd
 from app.features.memoir import repo as memoir_repo
 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,
@@ -49,7 +50,7 @@ async def _extract_and_store_image_intent(
             db, story.id, statuses=["pending", "failed"]
         )
         logger.debug(
-            "story image intent skipped: body below min chars story=%s len=%s min=%s",
+            "story image intent skipped: body below min chars story={} len={} min={}",
             story.id,
             len(plain),
             min_chars,
@@ -133,6 +134,7 @@ class StoryService:
             canonical_markdown=md,
         )
         await self._db.flush()
+        apply_infer_story_time_start_to_model(story)
         if md.strip():
             version = await create_story_version(
                 self._db,
@@ -160,11 +162,11 @@ class StoryService:
             try:
                 generate_story_image.delay(story.id)
             except Exception as exc:
-                logger.warning("派发 generate_story_image 失败: %s", 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: %s", exc)
+                logger.warning("派发 recompose_chapters_for_story 失败: {}", exc)
         return story.id
 
     async def append_version(
@@ -197,6 +199,7 @@ class StoryService:
         version.change_summary = change_summary
         story.current_version_id = version.id
         story.canonical_markdown = md
+        apply_infer_story_time_start_to_model(story)
         await _extract_and_store_image_intent(
             self._db,
             story=story,
@@ -211,11 +214,11 @@ class StoryService:
         try:
             generate_story_image.delay(story_id)
         except Exception as exc:
-            logger.warning("派发 generate_story_image 失败: %s", 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: %s", exc)
+            logger.warning("派发 recompose_chapters_for_story 失败: {}", exc)
         return version.id
 
     async def link_evidence(