Transition documentation from Office UI Fabric to Fluent UI

[Neutrino-Sunset]

Updated documentation to reflect the transition from Office UI Fabric to Fluent UI, including changes to project setup and component usage.

Category

• [ x] Content fix
• New article

Related issues

• fixes #issuenumber
• partially #issuenumber
• mentioned in #issuenumber

What's in this Pull Request?

Updated documentation to reflect the transition from Office UI Fabric to Fluent UI.
Updated sample code that no longer works.

[learn-build-service-prod]

PoliCheck Scan Report

The following report lists PoliCheck issues in PR files. Before you merge the PR, you must fix all severity-1 and severity-2 issues. The AI Review Details column lists suggestions for either removing or replacing the terms. If you find a false positive result, mention it in a PR comment and include this text: #policheck-false-positive. This feedback helps reduce false positives in future scans.

✅ No issues found

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[learn-build-service-prod]

Learn Build status updates of commit cb1adbb:

💡 Validation status: suggestions

File	Status	Preview URL	Details
docs/spfx/web-parts/get-started/use-fabric-react-components.md	💡Suggestion	View	Details

docs/spfx/web-parts/get-started/use-fabric-react-components.md

• Line 27, Column 3: [Suggestion: learn-site-link-broken - See documentation] Link '/javascript/api/office-ui-fabric-react' points to a learn site page that doesn't exist. Check the path or URL and update the link.

For more details, please refer to the build report.

Note: Your PR may contain errors or warnings or suggestions unrelated to the files you changed. This happens when external dependencies like GitHub alias, Microsoft alias, cross repo links are updated. Please use these instructions to resolve them.