Add legacy RN close recovery sweep

[ben-kaufman]

Summary

Adds a targeted recovery path for legacy React Native Bitkit wallets whose Blocktank cooperative-close outputs landed in native SegWit scripts derived from the selected legacy/wrapped address key paths.

What changed

• Added core scan and prepare-sweep APIs for the legacy RN native-segwit recovery flow.
• Scans the affected selected-address purposes as P2WPKH and prepares a signed sweep transaction to a caller-provided destination.
• Reuses the existing raw transaction broadcast API rather than adding a separate broadcast path.
• Added regression tests covering the affected derivation, signed sweep construction, and explicit zero-fee handling.
• Bumped bitkit-core to 0.1.63 and regenerated iOS/Android bindings.

Validation

• ./build.sh ios
• ./build.sh android
• cargo fmt
• git diff --check
• cargo test legacy_rn --lib
• cargo test sweep --lib

Also verified this branch is based on latest origin/master (8e49ab8) and that v0.1.63 was not already present on the remote before the bump.

[chatgpt-codex-connector]

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