WPB-22293 Remove Server response header value

[battermann]

Checklist

• Add a new entry in an appropriate subdirectory of changelog.d
• Read and follow the PR guidelines

[supersven]

LGTM 👍

[Copilot]

Pull request overview

This PR removes the HTTP Server response header value across services that use Network.Wai.Utilities.Server.newSettings, and aligns Stern’s domain-registration “get” endpoint behavior with Brig by propagating Brig’s HTTP status codes (notably 404 after deletion).

Changes:

• Clear Warp’s server name (setServerName "") in the shared WAI/Warp settings helper to avoid exposing a Server header value.
• Update Stern’s runClientToHandler to propagate status codes from servant-client FailureResponse (e.g., return 404 instead of 400).
• Switch Spar to the shared newSettings/defaultServer setup and adjust Stern integration test expectations accordingly.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tools/stern/test/integration/API.hs	Tightens assertion to expect 404 after domain-registration deletion.
tools/stern/src/Stern/Intra.hs	Propagates Brig status codes for servant-client FailureResponse errors.
services/spar/src/Spar/Run.hs	Uses shared WAI/Warp server settings (newSettings/defaultServer) instead of direct Warp settings.
libs/wai-utilities/src/Network/Wai/Utilities/Server.hs	Sets Warp server name to empty string to remove Server header value.
changelog.d/5-internal/WPB-22293	Changelog entry for Stern/Brig error propagation behavior.
changelog.d/3-bug-fixes/WPB-22293	Changelog entry for removing Server header value.

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