Docs: write final Create and Manage Wallets guide with screenshots

[johnny9]

Documentation Gap

The final v1.0 guide needs to reflect the release-scoped Create and Manage Wallets flows after implementation and parity decisions are complete.

Work Needed

• Update the Beta guide for the final v1.0 wallet lifecycle flow set.
• Capture final screenshots from the QML app.
• Include prerequisites, steps, expected results, and failure/recovery notes for the final flow set.
• Explicitly document any Qt widget wallet lifecycle behavior that is deferred after v1.0.

Priority

v1.0 / P2 secondary documentation requirement.