SDK & Tooling scaffolding (Rust sdk/, TS bindings/)

Scaffolded sdk/ and bindings/ts/.\n\nAction items:\n- [ ] Approve API surface for bq-sdk and @bitquan/sdk\n- [ ] Setup crates/pnpm workspaces + CI\n- [ ] Implement address + PSBT(PQC) per BQIP-0003\n- [ ] Conformance tests with node JSON-RPC