Publish to app blocked if httpnotify server is down during publish

[dcarrion87]

XIU version
For example: 0.13.0

Describe the bug

• When http notify server is down and publish stream connect error occurs and stream publishing is blocked until xiu server is restarted.

To Reproduce

• Configure http notify e.g.:

[httpnotify]
enabled = true
on_publish = "http://127.0.0.1/test/on_publish

• Try publish RTMP stream whilst http server is down
• Get connect error:

xiu[641]: [2025-04-26T11:59:37Z ERROR streamhub::notify::http] on_publish error: error sending request for url (http://127.0.0.1/test/on_publish): error trying to connect: tcp connect error: Connection refused (os error 111)

• Unable to publish to same stream app until xiu restart with this error:

Apr 26 12:01:27 0a2f6983a1e3 xiu[641]: [2025-04-26T12:01:27Z ERROR streamhub] event_loop Publish err: exists

Expected behavior

• There should be option to continue or recover regardless of http notify results. There are lots of time where http server may not be responsive.