Backporting for LTS 2.414.2

[krisstern]

Description

Fixed
-----

JENKINS-71479           Minor                   2.421
        Hovering over "Create" button to create a new credentials domain makes it invisible
        regression
        https://issues.jenkins.io/browse/JENKINS-71479

JENKINS-71366           Major                   2.417
        403 Forbidden on CSS stylesheet from same directory using HTML Publisher
        https://issues.jenkins.io/browse/JENKINS-71366

JENKINS-71238           Minor                   2.418
        New login page breaks login-theme-plugin (regression in 2.404)
        regression
        https://issues.jenkins.io/browse/JENKINS-71238

JENKINS-61452           Critical                2.420
        Illegal base64 character in FileLogStorage$1.writeHtmlTo(FileLogStorage.java:203)
        https://issues.jenkins.io/browse/JENKINS-61452

Before the changes are marked as ready-for-merge:

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1. There are at least two (2) approvals for the pull request and no outstanding requests for change.

   There are at least two (2) approvals for the pull request and no outstanding requests for change.
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2. Conversations in the pull request are over, or it is explicit that a reviewer is not blocking the change.

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3. Changelog entries in the pull request title and/or **Proposed changelog entries** are accurate, human-readable, and in the imperative mood.

   Changelog entries in the pull request title and/or Proposed changelog entries are accurate, human-readable, and in the imperative mood.
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4. Proper changelog labels are set so that the changelog can be generated automatically.

   Proper changelog labels are set so that the changelog can be generated automatically.
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5. If the change needs additional upgrade steps from users, the `upgrade-guide-needed` label is set and there is a **Proposed upgrade guidelines** section in the pull request title (see [example](https://github.com/jenkinsci/jenkins/pull/4387)).

   If the change needs additional upgrade steps from users, the upgrade-guide-needed label is set and there is a Proposed upgrade guidelines section in the pull request title (see example).
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6. If it would make sense to backport the change to LTS, a Jira issue must exist, be a _Bug_ or _Improvement_, and be labeled as `lts-candidate` to be considered (see [query](https://issues.jenkins.io/issues/?filter=12146)).

   If it would make sense to backport the change to LTS, a Jira issue must exist, be a Bug or Improvement, and be labeled as lts-candidate to be considered (see query).
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