Platform links lose their anchor when no platform is selected #20226

When no platform is active, PlatformLink points to /platform-redirect/?next=<encoded path>. If the target has an anchor, the # is encoded as %23 inside next. sanitizeNext in app/platform-redirect/utils.ts keeps only the path, so the redirect and the links on the platform selection page drop the anchor.

Steps to reproduce

1. Open https://docs.sentry.io/get-started/guides/issues-errors/ without a selected platform.
2. Select the ignoreErrors link. Its URL is /platform-redirect/?next=%2Fconfiguration%2Foptions%2F%23ignoreErrors.
3. Select a platform.

Or with curl:

curl -sI 'https://docs.sentry.io/platform-redirect/?next=/configuration/options/%23tracing-options&platform=python'

Expected result

The page opens at the ignoreErrors option (#ignoreErrors), and the redirect location ends with #tracing-options.

Actual result

The page opens at the top of Options, and the redirect location is /platforms/python//configuration/options/ with no fragment.

About 900 PlatformLink uses in the docs have an anchor.