fix(dashboard): 修复首页存储空间显示为 0

仪表板 _build_storage 原先仅按 library_storage 选取存储，用户只配置
本地下载目录而未填媒体库存储时存储集合为空，直接返回 0；而设置页经
LocalStorage.usage 同时统计下载目录与媒体库目录，故显示正常。

改为汇总下载目录的 storage 与媒体库目录的 library_storage，与 usage
口径对齐。存储名用 set 去重，同一存储只查询一次；磁盘层面 space_usage
已按 st_dev / Btrfs FSID 去重，相同磁盘的不同目录不会重复累加。

closes #6268

app/api/endpoints/dashboard.py

@@ -64,7 +64,13 @@ def _build_storage() -> schemas.Storage:
     dirs = DirectoryHelper().get_dirs()
     if not dirs:
         return schemas.Storage(total_storage=total, used_storage=total - available)
-    storages = set([d.library_storage for d in dirs if d.library_storage])
+    # 下载目录按 storage、媒体库目录按 library_storage 汇总存储集合，
+    # 用 set 去重存储名，避免同一存储被重复统计；
+    # 各存储的 usage 内部已按磁盘（st_dev / Btrfs FSID）去重，相同磁盘的不同目录不会重复累加。
+    storages = set(
+        [d.storage for d in dirs if d.download_path and d.storage]
+        + [d.library_storage for d in dirs if d.library_path and d.library_storage]
+    )
     for _storage in storages:
         _result = StorageChain().manage_storage(storage=_storage, action=StorageAction.USAGE.value)
         _usage = _result.get("data") if _result.get("success") else None

tests/test_dashboard_storage.py

@@ -0,0 +1,157 @@
+"""仪表板存储空间统计口径测试。
+
+覆盖 issue #6268：仪表板此前仅按 ``library_storage`` 选存储，
+只配置本地下载目录（未填媒体库存储）时会退化为 0，而设置页正常。
+"""
+from typing import Any, Dict, List
+from unittest.mock import patch
+
+from app import schemas
+from app.api.endpoints import dashboard as dashboard_endpoint
+from app.schemas.types import StorageAction
+
+
+def _usage_result(total: float, available: float) -> Dict[str, Any]:
+    """构造 storage_manage 契约的 usage 返回结构。"""
+    return {"success": True, "data": {"total": total, "available": available}}
+
+
+def _patch_dirs(dirs: List[schemas.TransferDirectoryConf]):
+    """替换仪表板读取的目录配置。"""
+    return patch.object(dashboard_endpoint.DirectoryHelper, "get_dirs", return_value=dirs)
+
+
+def test_storage_counts_local_download_dir_without_library_storage():
+    """只配置本地下载目录时仍应统计到该存储（issue #6268 回归）。"""
+    dirs = [
+        schemas.TransferDirectoryConf(
+            name="下载目录",
+            storage="local",
+            download_path="/downloads",
+        )
+    ]
+
+    with _patch_dirs(dirs), patch.object(
+        dashboard_endpoint.StorageChain,
+        "manage_storage",
+        return_value=_usage_result(1000.0, 400.0),
+    ) as mocked_usage:
+        ret = dashboard_endpoint._build_storage()
+
+    mocked_usage.assert_called_once_with(storage="local", action=StorageAction.USAGE.value)
+    assert ret.total_storage == 1000.0
+    assert ret.used_storage == 600.0
+
+
+def test_storage_queries_each_storage_once():
+    """同一存储被多个目录引用时只查询一次，避免重复累加。"""
+    dirs = [
+        schemas.TransferDirectoryConf(
+            name="下载与媒体库同盘",
+            storage="local",
+            download_path="/downloads",
+            library_path="/media",
+            library_storage="local",
+        ),
+        schemas.TransferDirectoryConf(
+            name="另一个本地目录",
+            storage="local",
+            download_path="/downloads2",
+            library_path="/media2",
+            library_storage="local",
+        ),
+    ]
+
+    with _patch_dirs(dirs), patch.object(
+        dashboard_endpoint.StorageChain,
+        "manage_storage",
+        return_value=_usage_result(1000.0, 400.0),
+    ) as mocked_usage:
+        ret = dashboard_endpoint._build_storage()
+
+    assert mocked_usage.call_count == 1
+    assert ret.total_storage == 1000.0
+    assert ret.used_storage == 600.0
+
+
+def test_storage_sums_distinct_storages():
+    """不同存储分别统计并累加。"""
+    dirs = [
+        schemas.TransferDirectoryConf(
+            name="本地下载",
+            storage="local",
+            download_path="/downloads",
+        ),
+        schemas.TransferDirectoryConf(
+            name="网盘媒体库",
+            storage="local",
+            download_path="/downloads",
+            library_path="/cloud/media",
+            library_storage="u115",
+        ),
+    ]
+    usages = {
+        "local": _usage_result(1000.0, 400.0),
+        "u115": _usage_result(500.0, 100.0),
+    }
+
+    with _patch_dirs(dirs), patch.object(
+        dashboard_endpoint.StorageChain,
+        "manage_storage",
+        side_effect=lambda storage, action: usages[storage],
+    ) as mocked_usage:
+        ret = dashboard_endpoint._build_storage()
+
+    assert {call.kwargs["storage"] for call in mocked_usage.call_args_list} == {"local", "u115"}
+    assert ret.total_storage == 1500.0
+    assert ret.used_storage == 1000.0
+
+
+def test_storage_skips_dirs_without_storage_fields():
+    """目录未填存储标识时不参与统计。"""
+    dirs = [
+        schemas.TransferDirectoryConf(name="空配置", download_path="/downloads"),
+        schemas.TransferDirectoryConf(name="空媒体库存储", library_path="/media"),
+    ]
+
+    with _patch_dirs(dirs), patch.object(
+        dashboard_endpoint.StorageChain, "manage_storage"
+    ) as mocked_usage:
+        ret = dashboard_endpoint._build_storage()
+
+    mocked_usage.assert_not_called()
+    assert ret.total_storage == 0
+    assert ret.used_storage == 0
+
+
+def test_storage_returns_zero_without_dirs():
+    """未配置任何目录时返回 0。"""
+    with _patch_dirs([]), patch.object(
+        dashboard_endpoint.StorageChain, "manage_storage"
+    ) as mocked_usage:
+        ret = dashboard_endpoint._build_storage()
+
+    mocked_usage.assert_not_called()
+    assert ret.total_storage == 0
+    assert ret.used_storage == 0
+
+
+def test_storage_ignores_failed_usage_result():
+    """存储查询失败时不计入统计。"""
+    dirs = [
+        schemas.TransferDirectoryConf(
+            name="下载目录",
+            storage="local",
+            download_path="/downloads",
+        )
+    ]
+
+    with _patch_dirs(dirs), patch.object(
+        dashboard_endpoint.StorageChain,
+        "manage_storage",
+        return_value={"success": False, "message": "该存储类型未启用或不支持此管理动作"},
+    ):
+        ret = dashboard_endpoint._build_storage()
+
+    assert ret.total_storage == 0
+    assert ret.used_storage == 0