feat: minimal sweep WIF QR-code implementation

[psychemist]

Description

This PR adds the ability to sweep funds from an external WIF private key into the user's wallet by scanning a QR code or copy-pasting the raw WIF string.

What This Does

• Scan a QR code containing a WIF private key (or type/paste it manually)
• App derives all standard address types (wpkh, pkh, tr, sh-wpkh) from the key, scans each for funds, and sweeps any balance into the user's wallet
• Supports mainnet (K/L/5) and testnet (c/9) WIF formats
• Accepts raw WIF, wif: prefix, and bitcoin:?wif= URI formats

Flow

• Send screen → "Sweep WIF" button → QR scanner dialog
• Scanned value parsed by WifParser.extract() and validated
• SendViewModel dispatches TransactionType.SWEEP on IO thread
• Wallet.sweep() iterates over descriptors, fully scans each via Esplora, and drains any with balance (confirmed + unconfirmed)
• Success/error toast via existing broadcastResult state flow

Testing

1. Unit tests (JVM, no device needed)
   ./gradlew :app:testDebugUnitTest

2. Install on device/emulator
   ./gradlew installDebug

3. Manual: send testnet4 coins to the wpkh address derived from a test WIF then sweep. Check in-app logs for balance details per descriptor.
   Check out test sweep transaction on testnet4 here:

Screenshots

[ItoroD]

@psychemist Hi thanks for the PR.

Not quite sure we want to add a WIF feature for the sample app. IMO adding WIF is a big jump from where the wallet is atm. @thunderbiscuit might have a different opinion.

Don't mind me asking, what was your rationale the for adding WIF ? are you use in your projects somewhere?

[reez]

have a contributor who added it for BDK iOS bitcoindevkit/BDKSwiftExampleWallet#355 so let me know if we're doing anything different from ya'll here if you do add it

[psychemist]

@ItoroD i saw the contribution on the iOS repo so i thought it would be a nice addition here. unfortunately, i thought about raising the issue AFTER i was done building

[ItoroD]

have a contributor who added it for BDK iOS bitcoindevkit/BDKSwiftExampleWallet#355 so let me know if we're doing anything different from ya'll here if you do add it

Ahhh I see! Thanks for the input.

[ItoroD]

@ItoroD i saw the contribution on the iOS repo so i thought it would be a nice addition here. unfortunately, i thought about raising the issue AFTER i was done building

No worries! When I saw camera permissions and QR scanning I had to look a little harder. I know IOS has been using those for a while already. I think we do not even have camera scanning for QR anywhere yet not even for scanning addresses. Probably good to start now. I will run the test and do a proper review.