fix(demos): use official Sui gRPC in browsers

[ducnmm]

Summary

• move Noter and Researcher browser clients to the official Sui gRPC transport
• configure NEXT_PUBLIC_SUI_GRPC_URL at image build time
• normalize object, dynamic-field, and transaction-change responses across gRPC and JSON-RPC fallback paths

Production incident

The default mainnet JSON-RPC endpoint rejects browser CORS preflights. The official Sui gRPC-Web service supports the required CORS paths, so both demos now use SuiGrpcClient against https://fullnode.mainnet.sui.io:443.

Validation

• Noter ESLint and TypeScript pass
• Researcher TypeScript passes
• live mainnet gRPC registry/dynamic-field lookup succeeds
• official gRPC-Web CORS preflights succeed
• production Noter bundle contains the official gRPC URL and no third-party RPC URL

[ducnmm]

@harrymove-ctrl Production Noter Google/Enoki login is currently blocked by the mainnet fullnode CORS policy. All required checks pass; could you please review this hotfix?