Implement NIP-62 Request to Vanish support

[alltheseas]

Summary

• Implement NIP-62 (Request to Vanish): Two-phase approach — writer thread sets a VanishPubkey marker instantly (blocking re-storage), cron thread sweeps and deletes events in batches every 30s to avoid long write locks. Deletes all authored events up to the vanish timestamp plus kind 1059 gift wraps addressed via p-tag. Kind 62 events are preserved for bookkeeping and protected from kind 5 deletion.
• Harden NIP-62: Add cfg().relay__nip62__enabled guard in writeEvents() so non-websocket paths (import, sync, router) respect the feature flag. Skip deletion index (tombstone) check for kind 62 events per spec: "Kind 5 deletion of a kind 62 event has no effect."
• Add writeTest cases: 6 tests covering vanish marker blocking, cross-pubkey isolation, kind 5 protection of kind 62, max-timestamp semantics, and boundary conditions.
• Add NIP-62 E2E websocket tests: 39 tests against a live strfry relay covering the full NIP-62 lifecycle — event submission, cron-based deletion sweep, re-broadcast prevention, relay tag validation, kind 5 protection (both orderings), deletion tombstone bypass via import path, gift wrap cleanup/blocking (ALL_RELAYS and specific serviceUrl), NIP-09 deletion event sweep, cross-pubkey isolation, timestamp boundaries, persistence across restart, NIP-11 advertisement, and feature flag behavior.

NIP-62 spec coverage

Spec requirement	Level	Test
Kind 62 deletes everything from .pubkey until .created_at	MUST	E2E: test_vanish_all_relays
Tag list MUST include at least one relay value	MUST	E2E: test_vanish_no_relay_tag_rejected
Relay MUST delete if its service URL is tagged	MUST	E2E: test_vanish_specific_relay
Relay SHOULD delete NIP-59 gift wraps p-tagged to pubkey	SHOULD	E2E: test_gift_wrap_deletion
Relay MUST prevent re-broadcast	MUST	E2E: test_vanish_all_relays, test_vanish_persists_after_restart
Relay MAY store the vanish event for bookkeeping	MAY	E2E: kind 62 preserved in all cron tests
Kind 5 against kind 62 has no effect	MUST	E2E: test_kind5_cannot_delete_kind62, test_kind5_tombstone_does_not_block_kind62
Global vanish via ["relay", "ALL_RELAYS"]	MUST	E2E: multiple tests
Delete everything including NIP-09 deletion events	MUST	E2E: test_nip09_deletion_events_swept

Test plan

• make test-subid — unit tests pass
• perl test/writeTest.pl — 36 tests pass (30 existing + 6 NIP-62)
• python3 test/nip62_e2e_test.py — 39 E2E tests pass (requires pip install secp256k1 websockets)
• Sync tests with generated test data pass

Closes #179

🤖 Generated with Claude Code

[alltheseas]

cc @jb55 @danieldaquino @kernelkind