Allowing Markdown in Pinned Messages

[rapterjet2004]

• fixes Sticky Message shows Markdown Code. #6233

🖼️ Screenshots

Screen_recording_20260529_131325.webm

• Wraps the Box with a CompositionLocalProvider to provide viewThemeUtils to the pinned message
• Adds a mapping function to ChatMessageUi to provide compatibility with the recently refactoring Chat View

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not needed
• 🔖 Capability is checked or not needed
• 🔙 Backport requests are created or not needed: /backport to stable-xx.x
• 📅 Milestone is set
• 🌸 PR title is meaningful (if it should be in the changelog: is it meaningful to users?)

[github-actions]

APK file: https://github.com/nextcloud/talk-android/actions/runs/26654235539/artifacts/7297966258
To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.
(please click on link to get QR code displayed)

[AndyScherzinger]

Argh, have been working on it as well in parallel but also changing the visuals and going for enriched text instead of full Markdown plus limiting it to 3 lines max 😂

What do we wanna do @rapterjet2004 @mahibi ?