fix(DeclarativeManager): Fix admin delegation

[marcelklehr]

The bug

• As admin, go to Settings → Admin Delegation
• Assign a group the following delegated sections: Basic Settings → Background Jobs and Basic Settings → Email Server
• Log in as a non-admin user who is a member of that group
• The navigation item "Basic Settings" appears in the admin menu

Expected behavior:

• The user can access the delegated admin sections.

Actual behavior:

• Navigating to /settings/admin returns "Access Denied". The navigation entry is rendered but the route does not grant access based on delegation permissions.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI

[marcelklehr]

/backport to stable34

[marcelklehr]

/backport to stable33

[marcelklehr]

/backport to stable32

[come-nc]

What is this fixing?

[marcelklehr]

Sorry, I added reproduction steps above.

[come-nc]

Declarative settings are incompatible with delegated settings and this PR correctly applies this restriction.
It would be a better fix to make them compatible but it’s a way bigger change.

Let’s get this in as it fixes access to other settings when some settings only are declarative ones.