If there is no storage proxy server, nothing will work.

## Summary  

[Provide a brief description of the bug.]  

- {width=1882 height=1480}
If there is no storage proxy server, nothing will work.
- Of course, storage proxy is an essential component of backend.ai .
However, it is strange that even the main page of backend.ai is not loaded without a storage proxy server.
We need to check which part is problematic.

## Steps to Reproduce  

[Outline the steps to consistently reproduce the issue.]  

1.
1.
1.

## Expected Behavior  

[Describe the expected result if the bug were resolved.]  

-

## Actual Behavior  

[Describe what actually happens when the bug occurs.]  

-

## Logs/Errors  

[Attach relevant logs, stack traces, or screenshots to help diagnose the issue.]  

- ```
Traceback (most recent call last):
File "/home/ubuntu/backend.ai/src/ai/backend/manager/server.py", line 277, in exception_middleware
resp = await handler(request)
^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/src/ai/backend/manager/server.py", line 264, in api_middleware
resp = await _handler(request)
^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/src/ai/backend/common/metrics/http.py", line 27, in metric_middleware
resp = await handler(request)
^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/src/ai/backend/manager/api/auth.py", line 593, in auth_middleware
return await handler(request)
^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/dist/export/python/virtualenvs/python-default/3.12.8/lib/python3.12/site-packages/aiotools/func.py", line 23, in wrapped
return await coro(*args, *cargs, **kwargs, **ckwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/src/ai/backend/manager/api/ratelimit.py", line 73, in rlim_middleware
response = await handler(request)
^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/dist/export/python/virtualenvs/python-default/3.12.8/lib/python3.12/site-packages/aiohttp/web_middlewares.py", line 117, in impl
return await handler(request)
^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/src/ai/backend/manager/api/auth.py", line 600, in wrapped
return await handler(request, *args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/src/ai/backend/manager/api/manager.py", line 79, in wrapped
return await handler(request, *args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/src/ai/backend/manager/api/utils.py", line 209, in wrapped
return await handler(request, checked_params, *args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/src/ai/backend/manager/api/vfolder.py", line 854, in list_hosts
all_volumes = await root_ctx.storage_manager.get_all_volumes()
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/src/ai/backend/manager/models/storage.py", line 170, in get_all_volumes
results = [*itertools.chain(*await asyncio.gather(*fetch_aws))]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/src/ai/backend/manager/models/storage.py", line 159, in _fetch
async with proxy_info.session.request(
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/dist/export/python/virtualenvs/python-default/3.12.8/lib/python3.12/site-packages/aiohttp/client.py", line 1360, in __aenter__
self._resp: _RetType = await self._coro
^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/dist/export/python/virtualenvs/python-default/3.12.8/lib/python3.12/site-packages/aiohttp/client.py", line 663, in _request
conn = await self._connector.connect(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/dist/export/python/virtualenvs/python-default/3.12.8/lib/python3.12/site-packages/aiohttp/connector.py", line 538, in connect
proto = await self._create_connection(req, traces, timeout)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/dist/export/python/virtualenvs/python-default/3.12.8/lib/python3.12/site-packages/aiohttp/connector.py", line 1050, in _create_connection
_, proto = await self._create_direct_connection(req, traces, timeout)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/dist/export/python/virtualenvs/python-default/3.12.8/lib/python3.12/site-packages/aiohttp/connector.py", line 1384, in _create_direct_connection
raise last_exc
File "/home/ubuntu/backend.ai/dist/export/python/virtualenvs/python-default/3.12.8/lib/python3.12/site-packages/aiohttp/connector.py", line 1353, in _create_direct_connection
transp, proto = await self._wrap_create_connection(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ubuntu/backend.ai/dist/export/python/virtualenvs/python-default/3.12.8/lib/python3.12/site-packages/aiohttp/connector.py", line 1124, in _wrap_create_connection
raise client_error(req.connection_key, exc) from exc
aiohttp.client_exceptions.ClientConnectorError: Cannot connect to host 127.0.0.1:6022 ssl:default [Connect call failed ('127.0.0.1', 6022)]
2025-07-22 05:05:39.240 INFO aiohttp.access [24458] 127.0.0.1 [22/Jul/2025:05:05:39 +0000] "GET /folders/_/hosts?group_id=2de2b969-1d04-48a6-af16-0bc8adb3c831 HTTP/1.1" 500 6433 "-" "Backend.AI Web Server 25.5.2"
```

JIRA Issue: BA-1939