[core] fix test_token_auth_integration on windows

[sampan-s-nayak]

Description

test_token_auth_integration is failing on windows as dashboard http agent seems to be failing to bind to a port (see attached logs). this pr switches to using dynamic port allocation to try and fix this problem

2026-01-06 08:09:33,356	ERROR http_server_agent.py:76 -- Agent port #52365 failed to bind after 6 attempts.
Traceback (most recent call last):
  File "C:\rayci\python\ray\dashboard\http_server_agent.py", line 50, in _start_site_with_retry
    await site.start()
  File "C:\Miniconda3\lib\site-packages\aiohttp\web_runner.py", line 121, in start
    self._server = await loop.create_server(
  File "C:\Miniconda3\lib\asyncio\base_events.py", line 1519, in create_server
    raise OSError(err.errno, 'error while attempting '
OSError: [Errno 10048] error while attempting to bind on address ('172.29.123.207', 52365): only one usage of each socket address (protocol/network address/port) is normally permitted
2026-01-06 08:09:33,356	ERROR agent.py:222 -- Failed to start HTTP server with exception: [Errno 10048] error while attempting to bind on address ('172.29.123.207', 52365): only one usage of each socket address (protocol/network address/port) is normally permitted. The agent will stay alive but the HTTP service will be disabled.
Traceback (most recent call last):
  File "C:\rayci\python\ray\dashboard\agent.py", line 213, in run
    await self.http_server.start(modules)
  File "C:\rayci\python\ray\dashboard\http_server_agent.py", line 120, in start
    site = await self._start_site_with_retry()
  File "C:\rayci\python\ray\dashboard\http_server_agent.py", line 83, in _start_site_with_retry
    raise last_exception
  File "C:\rayci\python\ray\dashboard\http_server_agent.py", line 50, in _start_site_with_retry
    await site.start()
  File "C:\Miniconda3\lib\site-packages\aiohttp\web_runner.py", line 121, in start
    self._server = await loop.create_server(
  File "C:\Miniconda3\lib\asyncio\base_events.py", line 1519, in create_server
    raise OSError(err.errno, 'error while attempting '
OSError: [Errno 10048] error while attempting to bind on address ('172.29.123.207', 52365): only one usage of each socket address (protocol/network address/port) is normally permitted

Related issues

Fixes anyscale#560

Additional information

Optional: Add implementation details, API changes, usage examples, screenshots, etc.

[gemini-code-assist]

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