deps: @noble v3, proven byte-identical on the signing path

[catomean]

@noble/secp256k1 2.3.0 → 3.1.0, @noble/hashes 1.8.0 → 2.3.0.

Both are breaking majors, and they land on the code that decides whether a
vote is real. So the interesting part of this PR is not the upgrade — it is
the evidence that it changed nothing.

The tests could not have caught a break

Every existing test signs and verifies with the same code. A change that
altered the wire format on both sides would have passed all fifteen of them
while silently invalidating every signature a real wallet produces — and every
signature already sitting in the audit trail.

Four known-answer tests now close that hole. All four were written and run
against v2 first, so they are known to hold before the upgrade rather than
fitted to it afterwards:

Test	What it anchors to
Address derivation	BIP173's own published vector. The key is secret exponent 1, so its public key is the secp256k1 generator and its P2WPKH address is the one written into the spec: bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4
Signed-message digest	Rebuilt from the spec inside the test rather than imported, compared byte for byte
Signature bytes	Asserted literally. RFC6979 makes signing deterministic, so the base64 is stable across versions unless nonce derivation or encoding moved
ECDSA validity	OpenSSL, via node:crypto, verifies it independently — the only check in the repo that isn't noble verifying noble

They pass unchanged on v3. The golden signature is the same base64, so every
signature already stored still verifies.

The API moves

• hmac wiring is now secp.hashes.{sha256,hmacSha256}, and hmacSha256
  takes a single message instead of varargs.
• sign() returns bytes, not a Signature. Recovery comes from
  format: 'recovered' (65 bytes, recovery || r || s), and prehash: false
  is load-bearing — the Bitcoin digest is already double-sha256, and letting
  the library hash again would sign the wrong value.
• Signature.fromCompact().recoverPublicKey() became the top-level
  recoverPublicKey(), so verification rebuilds the recovered encoding from
  the Bitcoin header || r || s layout.
• randomPrivateKey → randomSecretKey; secret keys are bytes now, not hex.
• @noble/hashes v2 moved its submodules: sha256 → sha2.js,
  ripemd160 → legacy.js, and every deep import needs the .js extension.

Verification

• npm run verify — exit 0 (37 passed, 2 skipped)
• npm run build — compiled successfully
• Golden signature base64 identical on v2 and v3; OpenSSL agrees on both