Port ImageCache from 7.x

**Source**: Microsoft.Toolkit.Uwp.UI.Helpers (7.x)
**Destination**: CommunityToolkit.WinUI.Helpers (8.x) — not yet ported

## Description

The ImageCache provides methods and tools to cache images in a temporary local folder.

## Prerequisites

None identified.

## Porting Basics

- [ ] Namespace updated to `CommunityToolkit.WinUI.*`
- [ ] Code for UWP, WinUI3 and Uno Platform consolidated
- [ ] Desired MultiTargets configured
- [ ] Sample code migrated
- [ ] Concept docs migrated
- [ ] Tests migrated and passing

## Quality Evaluation

See [Porting Criteria](https://github.com/CommunityToolkit/Windows/wiki/Component-Quality-Evaluation) for detailed evaluation guidance.

- [n/a] UX: Accessibility reviewed
- [n/a] UX: Visual design reviewed
- [n/a] UX: Interaction patterns appropriate
- [ ] DX: API surface reviewed
- [ ] DX: API flexibility appropriate
- [ ] DX: Documentation updated
- [ ] MX: Breaking changes documented
- [ ] MX: Domain isolation appropriate
- [ ] MX: Test coverage adequate

## Tracking Gaps

*No gaps identified — porting work not yet started.*

## Closing

- [ ] All Porting Basics complete
- [ ] Quality Evaluation reviewed
- [ ] Gaps filed as sub-issues

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## 7x Documentation Inventory

**Docs ported to 8x**: n/a

**Docs not in 8x**: All sections

## 7x Source Inventory

**Source already ported to 8x**: n/a

**Source not ported to 8x**: All

## Notes

- Not currently planned for porting. Open to community interest.
- **Archive redirect**: https://learn.microsoft.com/en-us/dotnet/communitytoolkit/windows/archive/imagecache

Inizia dalla documentazione archiviata di ImageCache e dai Porting Criteria collegati nell’issue, quindi esamina l’inventario completo del codice sorgente e della documentazione di 7.x. Il lavoro è completato quando il porting, gli esempi, la documentazione concettuale, i test, il multitargeting, la revisione dell’API e la checklist di valutazione della qualità sono completati.

Scritto dal modello di indicizzazione a partire dal testo della issue.