feat: minimal sweep WIF QR implementation

[otaliptus]

Description

This PR adds an example WIF sweep with a QR code (or copy-paste a raw WIF string). Given this is an example wallet app, I tried to keep the changes & functionality minimal.

The basic flow is as follows:

1. Using a regular wallet address A, go to Send part (i.e. QR scan)
2. Scan a WIF QR for B
3. It detects all sweepable funds at B and broadcasts a transaction that sweeps the funds to A

Best way to test it is generating a WIF/address and sending some funds there, and sweeping it. Some example transactions on testnet4 can be seen here.

I can also send the WIF of some addresses to Discord, in case you want to try.

Notes to the reviewers

I've tried to work clean here but let me know if you have an alternative implementation/flow in mind please. Also tried to use as much as existing features from BDK & FFI, but open to suggestions.

*Also I was having some problems with launching the wallet upon having an existin

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I have formatted my code with swift-format per .swift-format file

New Features:

• I've added tests for the new feature
• I've added docs for the new feature
• UI changes tested on small, medium, and large devices to ensure layout consistency