Domains Manage: Align empty state content with navigation header

[zaguiini]

Closes https://github.com/Automattic/wp-calypso/issues/96618.

Proposed Changes

Title. Align it with the stateful domains page.

Empty domains manage page

https://github.com/user-attachments/assets/bb1bb5c9-219b-4144-a765-63dc02f1933e

Stateful domains manage page

https://github.com/user-attachments/assets/c75b330d-a2e7-4cc6-a171-0e6eddcde600

Why are these changes being made?

Visual consistency.

Testing Instructions

Use two accounts to verify that the domains page with domains and the same page without share the same layout rules.

[github-actions[bot]]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-125288

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-125288&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-125288&env=a8c-for-agencies

[matticbot]

This PR modifies the release build for the following Calypso Apps:

For info about this notification, see here: PCYsg-OT6-p2

• notifications

To test WordPress.com changes, run install-plugin.sh $pluginSlug domains-manage/align-empty-state-content-with-navigation-header on your sandbox.

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Sections (~3 bytes added 📈 [gzipped])

``` name parsed_size gzip_size domains +85 B (+0.0%) +3 B (+0.0%) ``` Sections contain code specific for a given set of routes. Is downloaded and parsed only when a particular route is navigated to.

Legend

What is parsed and gzip size?

**Parsed Size:** Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory. **Gzip Size:** Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.