Personalization page entirely transparent when Aero is enabled

### Describe the bug

When using Windows Aero and the ESR 115 version of the theme and visiting the toolbar personalization page, Aero gets applied to the entire page, instead of just the titlebar.

### Expected behavior

The page should have white background (or black, if using dark theme), instead of a transparent one, as it does on the default theme and on earlier versions of this theme (tested on version 7.4.0).

### Screenshots

_No response_

### OS

Windows 7

### OS - Others

_No response_

### Firefox Version

115.14.0esr (32-bits)

### Distribution

- [ ] [Original Lepton](https://github.com/black7375/Firefox-UI-Fix)
- [X] [Lepton's photon style](https://github.com/black7375/Firefox-UI-Fix/tree/photon-style)
- [ ] [Lepton's proton style](https://github.com/black7375/Firefox-UI-Fix/tree/proton-style)

### Theme

- [ ] Light
- [ ] Dark
- [ ] Alpenglow (System: Light)
- [ ] Alpenglow (System: Dark)
- [X] System Default
- [ ] Others: (e.g. [Photon Colors](https://addons.mozilla.org/en-US/firefox/addon/photon-colors/), [Google Chrome Dark](https://addons.mozilla.org/en-US/firefox/addon/google-chrome-dark/), [Fairytale Of Nature](https://addons.mozilla.org/en-US/firefox/addon/fairytale-of-nature/))

### Theme - More Info

_No response_

### `user.js` setup

Tested on a new profile, default about:config and user.js used.

### Additional context

_No response_

Reproduce the issue on Windows 7 with Firefox 115.14.0esr, Windows Aero, and the photon-style theme while opening the toolbar personalization page. Trace the SCSS rules affecting that page and the titlebar, then verify that the page background is opaque white or dark rather than transparent in both relevant theme modes.

Written by the indexing model from the issue text.