Add Soroban deployment tooling, registry bootstrap, and unsigned XDR builder

[nottherealalanturing]

Summary

• add a contract registry module with publish, read, and rollback flows backed by Supabase with in-memory fallback and audit logging
• add testnet funding preflight + deployment planning services plus a Soroban CLI deploy script that emits artifacts and can auto-publish to the registry
• extend transaction building with unsigned XDR v1 idempotency, payload limits, and simulation summaries
• add focused unit coverage for the new registry, tooling, and transaction paths

Verification

• npm run test:unit -- src/contracts/contract-registry.service.unit.spec.ts src/soroban-tooling/soroban-tooling.unit.spec.ts src/transactions/transaction.service.unit.spec.ts
• npm run test:unit currently still fails in unrelated existing suites (for example bcrypt native loading on this machine, metrics expectations, and pre-existing ingestion/notification typing issues)
• npm run type-check currently still fails in unrelated existing analytics/ingestion/notification specs

Closes #502
Closes #503
Closes #504
Closes #505

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