add: GNS (.gwei) names support

[lucadonnoh]

What

Adds support for resolving GNS (Gwei Name Service) .gwei names, following the exact pattern Namoshi established: same ENS code path, different universal resolver contract.

GNS is an ownerless, ENS-compatible naming system on Ethereum (gwei.domains, source). Names are ERC-721 tokens keyed by EIP-137 namehash, registration fees are burned, and the contracts have no owner or admin.

How it plugs in

GNS ships a universal resolver implementing the same interface viem and EnsGetter already speak (resolveWithGateways / reverseWithGateways):

• GnsUniversalResolver: 0xD658131FFB6D732335d37f199374289F1b31564F, verified, stateless, no owner.
• Deployed at the same address on Ethereum mainnet and Sepolia, so defaultNetworksMode: 'testnet' works with no extra wiring.
• .gwei names live on the Ethereum provider already used for ENS. No new network, no new RPC provider.

Changes

• services/ensDomains: GNS_UNIVERSAL_RESOLVER const, getIsGweiDomain, isGweiDomain option on resolveENSDomain / reverseLookupEns / getEnsAvatar.
• controllers/domains: .gwei branch in resolveDomain, a third parallel lookup in #reverseLookup (batched through the existing deployless EnsGetter, which takes the resolver address as a parameter, so no contract changes), gwei field in the domains cache.
• interfaces/domains: gwei field on Domains entries, 'gwei' in resolvedAddressType.
• Tests: four new cases in domains.test.ts resolving a real mainnet name (donnoh.gwei) in both directions, plus the unregistered-name and no-name cases. Existing spy-count tests updated because each reverse refresh now performs two Ethereum lookups (ENS and GNS).

Behavior notes

• The GNS resolver signals "not found" with empty return values rather than reverts, so viem maps missing/expired names to null and EnsGetter treats them as hasName: false. No new error handling needed anywhere.
• Reverse records are forward-verified on-chain by GNS itself (a name that no longer resolves to the queried address is not returned).
• GNS is fully on-chain: no CCIP-read, gateways are ignored.

Verification

• npm run jest -- src/controllers/domains/domains.test.ts: 24/24 (the new tests hit the live mainnet deployment).
• npm run jest -- src/services/ensDomains/ensDomains.test.ts: 4/4.
• npm run type:check: no new errors (210 pre-existing on v2, identical with and without this change).
• npx eslint on the touched files: clean.

A companion PR adds the UI side (icon, input validation labels, account search) in the extension repo.