feat: Namecoin .bit NIP-05 identity verification

[mstrofnone]

Summary

Adds Namecoin blockchain-based NIP-05 identity verification for .bit domains. When a user's NIP-05 address ends in .bit (e.g. [email protected]), or uses Namecoin's d/ or id/ namespace, the app queries the Namecoin blockchain via ElectrumX servers instead of making HTTP requests.

Ported from Amethyst (MIT License, Vitor Pamplona).

New Files (12)

Core Services (lib/services/namecoin/)

• electrumx_server.dart — Data models, exception types, default server lists
• electrumx_client.dart — TCP/TLS client querying ElectrumX servers with fallback
• namecoin_name_resolver.dart — Parses identifiers and extracts Nostr pubkeys + relays
• namecoin_lookup_cache.dart — LRU cache with 1-hour TTL (500 entries max)
• namecoin_settings.dart — Settings model with custom ElectrumX server support
• namecoin_name_service.dart — App-level singleton: resolve(), verifyNip05(), resolvePubkey()
• namecoin_shared_preferences.dart — Persistence for enabled state + custom servers
• namecoin.dart — Barrel export file

UI

• settings_view/widgets/property_namecoin.dart — Settings list entry tile
• settings_view/widgets/namecoin_settings_view.dart — Full settings screen with enable/disable toggle, custom server management, and live test lookup
• widgets/nip05_namecoin_component.dart — Enhanced NIP-05 badge with chain-link icon for verified .bit identifiers

Tests

• test/services/namecoin/namecoin_name_resolver_test.dart — 24 unit tests covering identifier detection, settings parsing, and JSON value extraction

Modified Files (6)

• globals.dart — Added namecoinService and namecoinPreferences globals
• initializers.dart — Initialize Namecoin service on startup with graceful fallback
• http_functions_repository.dart — Route .bit domains to Namecoin verification
• metadata_cubit.dart — Route .bit identifiers to Namecoin resolution
• search_cubit.dart — Route .bit search queries through Namecoin resolver, skip relay connectivity check for .bit domains
• settings_view.dart — Add Namecoin settings tile

Supported Identifier Formats

Format	Example	Resolution
NIP-05 style	[email protected]	Look up d/example, find alice in names
Bare domain	example.bit	Look up d/example, use root entry
Domain namespace	d/example	Direct lookup, root entry
Identity namespace	id/alice	Direct lookup

Testing

• 24/24 unit tests pass
• Tested on Android emulator (Pixel 6, API 35) — search for [email protected] resolves correctly via ElectrumX
• No new dependencies — uses crypto (already in pubspec.yaml) and dart:io for TCP/TLS sockets