feat(send): add BNRP Bitcoin name resolution to send flow

[nlgal]

Summary

Adds Bitcoin name resolution to the BTC send flow via BNRP (BTC Name Resolution Protocol). Users can now type satoshi.btc, nakamoto.sats, or any supported Bitcoin name directly into the recipient field.

Spec: https://bnrp.name | API: https://api.bnrp.name/v1

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What changes

New file:

• src/app/hooks/useBnrpNameResolution.ts — resolution hook. Calls GET api.bnrp.name/v1/resolve/{name}, returns btc_taproot address (fallback: segwit, p2sh, legacy). Exposes resolve, reset, and typed resolution state (idle | resolving | resolved | error).

Modified file:

• src/app/components/recipientSelector/index.tsx — wires in useBnrpNameResolution. If the input matches a BNRP TLD, resolution runs before validateBtcAddress. Shows "Resolving..." feedback while in-flight. Displays resolved address on success. Falls back to normal address validation for raw BTC addresses.

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Supported TLDs

.btc .sats .x .ord .xbt .gm .unisat .sat

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UX

• Placeholder updated to: "Address or Bitcoin name (satoshi.btc)"
• While resolving: "Resolving satoshi.btc..." info feedback
• On success: resolved taproot address shown below input, onNext() fires automatically
• On failure: "Name not found" error feedback
• Button disabled + loading spinner during resolution
• Raw BTC addresses: unchanged behavior

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API

GET https://api.bnrp.name/v1/resolve/satoshi.btc

{
  "name": "satoshi.btc",
  "addresses": {
    "btc_taproot": "bc1p...",
    "btc_segwit": null
  }
}

No auth required. No new dependencies.

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Protocol extensions

BNRP also defines Lightning Address (BNRP-IP-09), Sign in with Bitcoin (BNRP-IP-10), AI Agent Namespace (BNRP-IP-11), Profile Records (BNRP-IP-12), and Sub-registry Delegation (BNRP-IP-13). Full spec at https://bnrp.name/adopt.html