fix: reject overlong UTXO swap memos before signing

[BitHighlander]

Summary

• make swap memo validation source-aware: 80 bytes for UTXO OP_RETURN, 250 bytes elsewhere
• skip overlong UTXO quotes during best-route selection instead of failing during device signing
• enforce the same rule during preview and execution
• replace the legacy signer wording with a clear route-refresh message in the swap UI
• add BTC → USDT and UTF-8 byte-length regression coverage

Root cause

Vault enforced only THORChain's global 250-byte memo limit, while the current KeepKey UTXO signer supports a single 80-byte OP_RETURN. A full contract-qualified BTC → USDT memo therefore passed quote parsing and preview, then failed late during signing.

User impact

Unbuildable UTXO routes now fail or fall through before the confirmation screen. No quoted memo is rewritten client-side; Pioneer remains responsible for constructing the compact protocol memo.

Validation

• bun test __tests__/swap-parsing.test.ts — 55 passed
• bunx vite build — passed
• git diff --check — passed

The repository-wide TypeScript check remains red on the existing baseline of unrelated errors; filtering its output to the touched files showed no new error at the changed lines.