feat: reintroduce TOKEN_REGISTRY_ENABLED flag (default disabled)
Clients rely on a runtime switch to turn token-registry enrichment on and off; the assets-ext refactor dropped it. Reintroduce a single flag, TOKEN_REGISTRY_ENABLED (default false), and route it through TokenQueryServiceImpl so disabled requests short-circuit to a policyId-only fallback without hitting the DB. Also revert the decimals-non-null contract from e5efb3b05: the disabled fallback now mirrors main (policyId only, subject/decimals null), so the mergeMetadata path no longer seeds decimals=0. Restored getDecimalsWithFallback in AccountMapperUtil and TransactionMapperUtils and flipped TokenRegistryCurrencyData.decimals back to @Nullable. Stripped the legacy HTTP-era flags (TOKEN_REGISTRY_BASE_URL, TOKEN_REGISTRY_CACHE_TTL_HOURS, TOKEN_REGISTRY_REQUEST_TIMEOUT_SECONDS) from every env template, docker-compose, Helm chart, CI workflow, and doc that still referenced them. Enabled token registry + logo on preprod (.env.docker-compose-preprod, values-preprod.yaml). Rewrote docs/docs/advanced-configuration/token-metadata.md to describe the new DB-backed yaci-store assets-ext flow instead of the removed cf-token-metadata-registry HTTP proxy setup. Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>