fix(resources): enforce visibility on list + get (private invisible to non-owner)

回退 5483d19 的 workspace-wide 改动。用户真实语义：
- owner 永远可见自己的资源（含 private）
- 非 owner 只见别人 visibility in {workspace, public} 的资源
- admin 全部可见

can_view 与 list_resources 共享同一谓词。list 端点恢复
owner == me OR visibility in {workspace, public} 的过滤，
admin 跳过。get_resource / download_url / jupyter-relative-path
/ delete_resource 全部经 get_visible_resource → can_view，自然
收敛到同一语义。补 1 个 owner-看自己-private 测试，4 个
visibility 测试保持。

backend/src/backend/resources.py

@@ -20,7 +20,7 @@ from common.storage.schemas import (
     DownloadUrlRequest,
 )
 from fastapi import APIRouter, Depends, Header, HTTPException, Query, Request, status
-from sqlalchemy import func, select
+from sqlalchemy import func, or_, select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from backend.dependencies import (
@@ -148,10 +148,14 @@ def resource_payload(
 
 
 def can_view(resource: DataResources, context: RequestContext) -> bool:
-    # 2026-08-11: 同一 workspace 内成员可以查看彼此的资源（含 private）；
-    # 保留 visibility 字段仅作为上传/绑定时的语义标签，不再影响读取。
-    # 还原: 加回 owner_user_id 检查。
-    return True
+    # 同一 workspace 内：owner 永远可见自己的资源（含 private）；
+    # 其他成员只见 visibility in {workspace, public} 的资源；
+    # admin 全部可见。
+    if resource.owner_user_id == context.user.user_id:
+        return True
+    if resource.visibility in {"workspace", "public"}:
+        return True
+    return context.is_admin
 
 
 # 根据当前脚本位置计算资源的相对路径，便于 Notebook 中用相对路径读取文件。
@@ -413,16 +417,16 @@ async def list_resources(
                 escape="\\",
             ),
         )
-    # 2026-08-11: 临时取消"用户间目录互相不可见"约束
-    # 列表接口现在返回 workspace 内全部 active 资源(不再按 owner / visibility 过滤)。
-    # 还原: 删除下面这段注释,恢复原来的 if not context.is_admin: ... 块。
-    # if not context.is_admin:
-    #     statement = statement.where(
-    #         or_(
-    #             DataResources.owner_user_id == context.user.user_id,
-    #             DataResources.visibility.in_(["workspace", "public"]),
-    #         )
-    #     )
+    # 只返回 owner 自己的资源（含 private），或 visibility 为
+    # workspace/public 的其他成员资源；A 的 private 资源对非 owner 不可见。
+    # admin 跳过过滤，全部可见。
+    if not context.is_admin:
+        statement = statement.where(
+            or_(
+                DataResources.owner_user_id == context.user.user_id,
+                DataResources.visibility.in_(["workspace", "public"]),
+            )
+        )
     if visibility:
         if visibility not in {"private", "workspace", "public"}:
             raise HTTPException(

backend/tests/test_resources.py

@@ -420,13 +420,14 @@ def _resource_ctx(workspace_id: str = "W001") -> SimpleNamespace:
         request_id="test",
         user=SimpleNamespace(user_id="U001"),
         workspace=SimpleNamespace(workspace_id=workspace_id),
+        is_admin=False,
     )
 
 
-class TestCanViewWorkspaceWideVisibility:
-    """can_view is workspace-wide: any workspace member may view any active
-    resource, matching list_resources since 2026-08-11. visibility is only a
-    semantic tag on upload/bind and no longer gates reads."""
+class TestCanViewVisibility:
+    """同一 workspace 内：owner 永远可见自己的资源（含 private）；
+    其他成员只见 visibility in {workspace, public} 的资源；
+    admin 全部可见。与 list_resources 的 SQL 谓词一致。"""
 
     @staticmethod
     def _viewer() -> SimpleNamespace:
@@ -437,9 +438,15 @@ class TestCanViewWorkspaceWideVisibility:
             is_admin=False,
         )
 
+    @staticmethod
+    def _owner() -> SimpleNamespace:
+        ctx = TestCanViewVisibility._viewer()
+        ctx.user = SimpleNamespace(user_id="U001")  # the owner
+        return ctx
+
     @staticmethod
     def _admin() -> SimpleNamespace:
-        ctx = TestCanViewWorkspaceWideVisibility._viewer()
+        ctx = TestCanViewVisibility._viewer()
         ctx.is_admin = True
         return ctx
 
@@ -449,13 +456,22 @@ class TestCanViewWorkspaceWideVisibility:
         res.visibility = visibility
         return res
 
-    def test_workspace_member_can_view_others_private_resource(self) -> None:
+    def test_owner_can_view_own_private_resource(self) -> None:
+        assert (
+            can_view(
+                self._resource("private"),
+                self._owner(),
+            )
+            is True
+        )
+
+    def test_workspace_member_cannot_view_others_private_resource(self) -> None:
         assert (
             can_view(
                 self._resource("private"),
                 self._viewer(),
             )
-            is True
+            is False
         )
 
     def test_workspace_member_can_view_others_workspace_resource(self) -> None: