docs: add comprehensive Xamarin.Forms migration guides (backport #22526)

[mergify]

• Review existing Xamarin.Forms migration documentation structure
• Create data-binding.md migration guide
• Create effects.md migration guide
• Create animations.md migration guide
• Create custom-drawn-controls.md migration guide
• Create custom-controls.md migration guide
• Create control-mappings.md with comprehensive control reference
• Create navigation.md based on blog post content
• Create native-controls.md covering renderers and bindings
• Update toc.yml to reference all new local pages
• Update overview.md "What's covered" section to link to all pages
• Verify all UIDs are consistent and cross-links work
• Validate documentation structure
• Check for conflicts with existing content
• Review phrasing for XF migration context
• Fix Microsoft Learn API links (Frame, NavigationView)
• Complete comprehensive API review per Microsoft docs

Original prompt

Update Uno Platform documentation to add/refresh Xamarin.Forms migration content based on issue https://github.com/unoplatform/private/issues/342.

Repository: unoplatform/uno

Goals:

1. Review existing Xamarin.Forms migration docs and ensure accuracy.

2. Add new first-class documentation pages (in-repo markdown) derived from the following blog posts referenced by the issue:

   • https://platform.uno/blog/xamarin-forms-migration-to-uno-platform-data-binding-techniques/
   • https://platform.uno/blog/xamarin-forms-migration-to-uno-platform-effects-and-alternative-approaches/
   • https://platform.uno/blog/migrating-animations-from-xamarin-forms-to-uno-platform/
   • https://platform.uno/blog/porting-a-custom-drawn-xamarin-forms-control-to-uno-platform/
   • https://platform.uno/blog/porting-custom-controls-from-xamarin-forms-to-uno-platform/
     (Ensure all content is accurate for current Uno Platform versions and templates.)

3. Update navigation so the docs point to these new pages instead of external blog links:

   • Update doc/articles/guides/xf-migration/toc.yml to reference the new pages using xref or local href.
   • Update doc/articles/guides/xf-migration/overview.md “What’s covered” section to link to the new pages.

4. Ensure doc build metadata is correct:

   • Add proper front-matter uid: for new docs pages under the Uno.XamarinFormsMigration.* namespace.
   • Use consistent headings and cross-links between pages (Overview -> Intro -> topic pages).

5. Follow repository conventions:

   • Prefer existing doc patterns and any repo docs guidelines.
   • Keep changes scoped to documentation.

PR description requirements:

• Include a 1–3 sentence summary explaining what/why/which issue.
• Include the mandatory issue footer using fully qualified link:
  Related to https://github.com/unoplatform/private/issues/342

Commit message must follow Conventional Commits, likely:

• docs: add Xamarin.Forms migration guides

Acceptance criteria:

• New markdown docs pages exist for Data Binding, Effects, Animations, Custom Controls, and Custom-Drawn Controls.
• xf-migration TOC and overview no longer link out to the blog posts for those items.
• Links build correctly (xref/uid works) and the docs are internally navigable.

This pull request was created from Copilot chat.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

---

This is an automatic backport of pull request #22526 done by Mergify.

[mergify]

Cherry-pick of 22f6339 has failed:

On branch mergify/bp/release/stable/6.5/pr-22526
Your branch is ahead of 'origin/release/stable/6.5' by 19 commits.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit 22f6339ee6.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   build/cSpell.json

no changes added to commit (use "git add" and/or "git commit -a")

Cherry-pick of 2c73337 has failed:

On branch mergify/bp/release/stable/6.5/pr-22526
Your branch is ahead of 'origin/release/stable/6.5' by 23 commits.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit 2c73337eb4.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   build/cSpell.json

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
2 out of 3 committers have signed the CLA.

✅ Jen-Uno
✅ ajpinedam
❌ Copilot
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[unodevops]

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-22557/docs/index.html