Some issues with QPushButtons custom stylesheet's padding (Windows)

Testing on Anki 25.08 beta 5. Also reproducible as far back as ~ 2.1.55/2.1.56.

`Stylesheet.py` uses this custom styling

```
def button(self, tm: ThemeManager) -> str:
# For some reason, Windows needs a larger padding to look the same
button_pad = 25 if is_win else 15
return f"""
QPushButton {{ padding-left: {button_pad}px; padding-right: {button_pad}px; }}
```

I believe this code may be an updated version of the one found in [this PR](https://github.com/ankitects/anki/pull/2115), intended to address the same issue - namely, as a workaround to increase the width of the **Help**, **Add**, **History**, and **Close** buttons in the Add window.

This works well for the most part, but it also introduces some issues, particularly with certain add-ons. Since this is a static CSS rule, it doesn’t account for the actual space available around the buttons.

For example, the extra padding may reduce the space available for button icons or placeholders.

---

**[Advanced Copy Fields](https://ankiweb.net/shared/info/1898445115)** — affected button: the one with the `>>` symbol, second line from the top.

1. **Current custom stylesheet** (the `>>` symbol is missing):

2. **After disabling**
`QPushButton {{ padding-left: {button_pad}px; padding-right: {button_pad}px; }}`:

3. **After disabling all `QPushButton` custom styles** (using Fusion as the Qt style):

---

**[Searching PDF Reading and Note-Taking in Add Dialog (Fixed by Shigeඞ)](https://ankiweb.net/shared/info/1250212877)**

1. **Current custom stylesheet** (the labels of the buttons at the bottom of the screen are clipped on both sides, making them unreadable):

2. **After disabling**
`QPushButton {{ padding-left: {button_pad}px; padding-right: {button_pad}px; }}`:

3. **After disabling all `QPushButton` custom styles** (using Fusion as the Qt style):

---

Start in Stylesheet.py at the QPushButton padding rule and reproduce the reported behavior on Windows with the Advanced Copy Fields and PDF Reading add-ons. Compare the Help, Add, History, Close, and add-on buttons; done means the intended button sizing remains while icons, placeholders, and labels are not clipped or missing.

Written by the indexing model from the issue text.