fix(QExpansionItem): switch-toggle-side colors are now correct

[Jadu07]

What kind of change does this PR introduce?

• Bugfix
• Feature
• Documentation
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change?

• Yes
• No

The PR fulfills these requirements:

• It's submitted to the dev branch (or v[X] branch)
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix: #xxx[,#xxx], where "xxx" is the issue number)
• It's been tested on a Cordova (iOS, Android) app
• It's been tested on an Electron app
• Any necessary documentation has been added or updated in the docs or explained in the PR's description.

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to start a new feature discussion first and wait for approval before working on it)

Other information:

When using switch-toggle-side on QExpansionItem with an :icon prop, the icon turns grey and the expand arrow turns black — the opposite of expected.

The side/avatar props on the icon's QItemSection were inverted in getHeaderChild():

// ui/src/components/expansion-item/QExpansionItem.js
- side: props.switchToggleSide === true,
- avatar: props.switchToggleSide !== true
+ side: props.switchToggleSide !== true,
+ avatar: props.switchToggleSide === true

This restores the correct colours: icon stays full-colour (avatar), expand arrow stays secondary/grey (side), regardless of which side they're on.

closes #18008

[github-actions]

UI Tests Results

    1 files     98 suites   40s ⏱️
1 031 tests 1 031 ✅ 0 💤 0 ❌
1 050 runs  1 050 ✅ 0 💤 0 ❌

Results for commit 7da2387.

[IceIsFrozen]

Here's the original problem:

The suggested change you made breaks original and switched versions as seen during testing. The original has no solid color and the switched has two bolded. An indentation issue also appears with the change.

If you utilize the PR suggested earlier that covers both scenarios to get the desired results.

[Jadu07]

@IceIsFrozen Thanks for pointing that out! The layout issue happened because the JS props were changed.

I’ve reverted the .js changes and pushed a CSS-only fix (QExpansionItem.sass). It swaps the colors using :has() without affecting the layout, so the indentation stays correct.

[Jadu07]

@rstoenescu @yusufkandemir pls review this pr