fix: 将平台业务ID统一改为String并自动建表

- 抖音、B站、快手、微博的帖子/视频/评论ID从BigInteger改为String，
  避免PostgreSQL下字符串写入BIGINT报错及未来ID溢出风险
- B站dynamic_id改为String，修复API返回id_str被强转int导致的精度丢失
- 知乎提取器对content_id/question_id显式str()转换
- main.py启动数据库保存模式时自动建表，无需手动--init_db
- 同步更新相关老化测试

store/weibo/_store_impl.py

@@ -118,8 +118,7 @@ class WeiboDbStoreImplement(AbstractStore):
         """
         # 教学版兜底：过滤掉已删除/多余字段，确保不会把 user_id/avatar 等传给 ORM
         content_item = _filter_model_fields(WeiboNote, content_item)
-        note_id = int(content_item.get("note_id"))
-        content_item["note_id"] = note_id
+        note_id = content_item.get("note_id")
         async with get_session() as session:
             stmt = select(WeiboNote).where(WeiboNote.note_id == note_id)
             res = await session.execute(stmt)
@@ -147,9 +146,7 @@ class WeiboDbStoreImplement(AbstractStore):
         """
         # 教学版兜底：过滤掉已删除/多余字段，确保不会把 user_id/avatar 等传给 ORM
         comment_item = _filter_model_fields(WeiboNoteComment, comment_item)
-        comment_id = int(comment_item.get("comment_id"))
-        comment_item["comment_id"] = comment_id
-        comment_item["note_id"] = int(comment_item.get("note_id", 0) or 0)
+        comment_id = comment_item.get("comment_id")
         comment_item["create_time"] = int(comment_item.get("create_time", 0) or 0)
         comment_item["comment_like_count"] = str(comment_item.get("comment_like_count", "0"))
         comment_item["sub_comment_count"] = str(comment_item.get("sub_comment_count", "0"))