Docs: write Beta Settings and Help user guide

[johnny9]

Documentation Gap

Beta needs user-facing documentation for the Settings and Help flows that are available in the app. Documentation is not required for Preview.

Work Needed

• Document Settings navigation.
• Document AboutPage and external links.
• Document visible Display settings.
• Document visible Connection/proxy settings.
• Document visible Storage/window/developer settings that remain available for Beta.
• Add Beta screenshots.

Priority

Beta / P2.