feat(nostr): nostr-based account registration and verification

Rebuilt the nostr registration feature cleanly on top of current ergo
mainline (origin/master), dropping the stale ergo reversions that were
entangled in the original squashed branch.

- New irc/nostr package: NIP-04/NIP-17 DMs, NIP-05 resolution, relay
  connect/auth, and identifier helpers.
- Registration/verification via nostr: parseCallback auto-detects nostr
  identifiers (NIP-05, npub, hex pubkey) and dispatches a verification DM.
- Nostr-based cloaked hostnames for accounts (opt-in via
  ip-cloaking.nostr-hostnames), applied at the account-cloak sites.
- Config: accounts.registration.nostr-verification and the
  nostr-hostnames cloak option, with matching default.yaml and help text.
- Adds github.com/nbd-wtf/go-nostr and vendored dependencies.

vendor/github.com/coder/websocket/make.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+set -eu
+cd -- "$(dirname "$0")"
+
+echo "=== fmt.sh"
+./ci/fmt.sh
+echo "=== lint.sh"
+./ci/lint.sh
+echo "=== test.sh"
+./ci/test.sh "$@"
+echo "=== bench.sh"
+./ci/bench.sh