fix(realunit): defer Config read in pricing service to avoid bootstrap crash

[TaprootFreak]

Summary

PricingRealUnitService read Config.environment in a class field initializer. Because of a circular import between this service and src/config/config, the Config singleton is undefined at construction time, so NestJS DI threw:

TypeError: Cannot read properties of undefined (reading 'environment')
  at new PricingRealUnitService (.../pricing-realunit.service.ts)

This happened during DI instantiation, so the whole API failed to bootstrap (crash loop, all health endpoints down on DEV).

Root cause

The recently added field:

private readonly tokenBlockchain = [Environment.DEV, Environment.LOC].includes(Config.environment)
  ? Blockchain.SEPOLIA : Blockchain.ETHEREUM;

Environment (an enum) resolves fine, but the Config value is assigned later and is still undefined when the field initializer runs under the import cycle.

Fix

Convert tokenBlockchain into a lazy getter so the Config read is deferred to runtime, after the module graph is fully initialized. The value is only consumed at runtime (getLastKnownPrice), so behavior is unchanged.

Local checks (npm ci, all green)

• lint ✅ · format:check ✅ · build ✅ · test (75 suites, 1009 tests) ✅ · npm audit --audit-level=critical ✅

Test plan

• Targeted spec pricing-realunit.service.spec.ts passes (4/4)
• Full unit-test suite green