fix(drivers/github_releases): skip broken repos instead of returning 500

[xrgzs]

Summary / 摘要

When multiple repos are configured and one fails (404, rate limit, etc.), the driver now logs a warning and skips that repo instead of panicking with a nil pointer dereference that caused a 500 error for the entire storage. Added proper error propagation from GetRequest through RequestRelease/RequestReleases/GetOtherFile, and nil checks on all Release/Releases dereferences.

Instead of hiding broken repos entirely, still display them as directory entries in parent listings. Return an error only when the user navigates into a broken repo.

背景

挂载好多个仓库（如下），访问挂载的根目录， 报错 500，也没有报错信息。发现是 uv 有问题，删了 astral-sh 那两个就正常。说明 OpenList 没有跳过错误，在挂载多个仓库时，这样会使其他本来能访问的仓库也无法访问，体验不好。

frp:fatedier/frp
amlogic-s9xxx-armbian:ophub/amlogic-s9xxx-armbian
EasyTier:EasyTier/EasyTier
rclone:rclone/rclone
uv:astral-sh/uv
python-build-standalone:astral-sh/python-build-standalone
FFmpeg-Builds:KarinJS/FFmpeg-Builds

• This PR has breaking changes.
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• This PR changes public API, config, storage format, or migration behavior.
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