fix: 使用正确的广场接口 /business/square/list

问题根因：
- 一直用 /business/member/square/list（成员广场接口）
- 该接口加了 isPlatformShow=true 和 isAdmin=false 过滤
- 导致大量文章（包括今日最新文章）被过滤掉，只剩124篇
- 正确接口 /business/square/list?type=1 有2504篇文章，今日文章可见

修改内容：
1. 接口地址改为 /business/square/list（4处）
2. 去掉 isPlatformShow 和 isAdmin 参数，只保留 type=1
3. _is_today 时间字段优先用 publishTime（新接口主要返回此字段）
4. 排序和热度权重计算也统一用 publishTime 优先

backend/app/services/news_service.py

@@ -401,9 +401,11 @@ class NewsPlatformService:
         } | news_service._invalid_ids_cache
 
         def _build(page, size=50):
+            # Use /business/square/list (not /business/square/list)
+            # Only type=1 filter — isPlatformShow/isAdmin exclude org-less articles
             p = self._build_form({
                 "pageNum": page, "pageSize": size,
-                "type": "1", "isPlatformShow": "true", "isAdmin": "false",
+                "type": "1",
             }, cfg)
             if org_id:
                 p["orgId"] = org_id
@@ -421,7 +423,8 @@ class NewsPlatformService:
             return items
 
         def _is_today(item):
-            t = item.get("createTime") or item.get("publishTime") or ""
+            # API returns publishTime (not createTime) for /business/square/list
+            t = item.get("publishTime") or item.get("createTime") or item.get("pushTime") or ""
             if not t:
                 return False
             try:
@@ -436,7 +439,7 @@ class NewsPlatformService:
             async with httpx.AsyncClient(timeout=12) as c:
                 for page in range(1, 4):   # 第1页最新，逐页往前
                     r = await c.get(
-                        f"{biz}/business/member/square/list",
+                        f"{biz}/business/square/list",
                         headers=self._bearer(token),
                         params=_build(page),
                     )
@@ -463,7 +466,7 @@ class NewsPlatformService:
         if today_articles:
             # 今日文章：从新到旧排序（createTime 降序）
             today_articles.sort(
-                key=lambda x: x.get("createTime") or x.get("publishTime") or "",
+                key=lambda x: x.get("publishTime") or x.get("createTime") or x.get("pushTime") or "",
                 reverse=True
             )
             # 去重（按 recordId）
@@ -502,7 +505,7 @@ class NewsPlatformService:
         try:
             async with httpx.AsyncClient(timeout=10) as _c:
                 _r = await _c.get(
-                    f"{biz}/business/member/square/list",
+                    f"{biz}/business/square/list",
                     headers=self._bearer(token),
                     params=_build(1),
                 )
@@ -537,7 +540,7 @@ class NewsPlatformService:
                 try:
                     async with httpx.AsyncClient(timeout=15) as c:
                         r = await c.get(
-                            f"{biz}/business/member/square/list",
+                            f"{biz}/business/square/list",
                             headers=self._bearer(token),
                             params=_build(page),
                         )