[UI Tests] Replace pixel-by-pixel image comparison with perceptual hash (pHash) for improved visual similarity detection (#40653)

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fix/what does it change/how was it tested (even manually, if necessary)?
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## Summary of the Pull Request
This PR replaces the previous pixel-by-pixel image comparison logic with
a perceptual hash (pHash)-based comparison using the
CoenM.ImageSharp.ImageHash library.

**Removes the need for golden images from CI pipelines**
Since the comparison is perceptual rather than binary, we no longer need
to fetch pixel-perfect golden images from pipelines for validation.
Developers can now capture screenshots locally and still get meaningful,
robust comparisons.

### Why pHash?
Unlike direct pixel comparison (which fails on minor rendering
differences), pHash focuses on the overall structure and visual
perception of the image. This provides several benefits:

- Robust to minor differences: tolerates compression artifacts,
anti-aliasing, subtle rendering changes, and border padding.
- Resilient to resolution or format changes: works even if images are
scaled or compressed differently.
- Closer to human perception: more accurately reflects whether two
images "look" the same to a person.

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## PR Checklist

- [ ] **Closes:** #xxx
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

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## Detailed Description of the Pull Request / Additional comments

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wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

Directory.Packages.props

@@ -9,6 +9,7 @@
     <PackageVersion Include="Microsoft.Bot.AdaptiveExpressions.Core" Version="4.23.0" />
     <PackageVersion Include="Appium.WebDriver" Version="4.4.5" />
     <PackageVersion Include="Azure.AI.OpenAI" Version="1.0.0-beta.17" />
+    <PackageVersion Include="CoenM.ImageSharp.ImageHash" Version="1.3.6" />
     <PackageVersion Include="CommunityToolkit.Common" Version="8.4.0" />
     <PackageVersion Include="CommunityToolkit.Mvvm" Version="8.4.0" />
     <PackageVersion Include="CommunityToolkit.WinUI.Animations" Version="8.2.250402" />