把“章节正文 + 图片”从 chapters 单表/JSON 结构，重构为“章节 chapter + 段落 section + 图片 memoir_images 独立表”的新数据模型，同时联动修改接口、PDF 导出、异步任务、迁移脚本、测试，以及修复 Android 端聊天列表显示问题。 (#9)

* refactor: 表结构重构，新增段落section和图片image新表

* fix: fix android app import error

* refactor: 重构文件名

* fix: 优化提示词

* fix: 消息气泡显示位置异常问题

---------

Co-authored-by: yangshilin <2157598560@qq.com>

api/services/memoir_images/parser.py

@@ -52,3 +52,33 @@ def build_initial_image_assets(
         }
         for item in placeholders
     ]
+
+
+def split_narrative_to_sections(narrative: str) -> list[dict[str, Any]]:
+    """
+    将带 {{IMAGE:...}} 占位符的正文按占位符拆成多段。
+    返回 list[dict]，每项含:
+    - content: 本段纯文本（不含占位符）
+    - placeholder_info: 本段后的配图占位信息，或 None（最后一段无图）
+    """
+    if not (narrative or narrative.strip()):
+        return []
+    placeholders = parse_image_placeholders(narrative, max_images=None)
+    sections: list[dict[str, Any]] = []
+    for i in range(len(placeholders) + 1):
+        if i == 0:
+            start = 0
+        else:
+            prev = placeholders[i - 1]
+            start = prev["start_offset"] + len(prev["placeholder"])
+        if i < len(placeholders):
+            end = placeholders[i]["start_offset"]
+            placeholder_info = placeholders[i]
+        else:
+            end = len(narrative)
+            placeholder_info = None
+        content = narrative[start:end]
+        if isinstance(content, str):
+            content = content.strip()
+        sections.append({"content": content or "", "placeholder_info": placeholder_info})
+    return sections