Page and app configuration UI is not migrated to the new design

[CharlesGrimont]

The page and app configuration UI has not been migrated to the new design yet.

Current behavior:

• Page configuration still uses the previous design.
• App configuration still uses the previous design.
• This creates an inconsistent experience compared with the rest of the updated editor UI.

Expected behavior:

• Page configuration should follow the new design.
• App configuration should follow the new design.
• The configuration UI should be visually and functionally consistent with the rest of the editor.

Acceptance criteria:

• Page configuration UI is migrated to the new design.
• App configuration UI is migrated to the new design.
• Existing configuration options remain available and functional.
• No regression on saving, loading, or applying page/app configuration changes.

[github-actions]

To be tested in 2.2.0-beta112

[gregory-vorbe]

Labels are not translated:

[github-actions]

To be tested in 2.2.0-beta113

[gregory-vorbe]

OK in 2.2.0-beta114