feat(operator): configure Ledger v3 NATS sinks

[flemzord]

Summary

• pin the Ledger Operator API from feat(operator): reconcile NATS event sinks ledger#1844 and expose the sink fields in LedgerConfiguration
• configure a reserved Ledger v3 NATS sink when the ledger BrokerTopic is ready, while preserving explicitly configured sinks
• extend NATS streams and consumers with descendant subjects and migrate existing resources through revisioned idempotent Jobs
• preserve existing exact subjects for v2 publishers and consumers
• require the installed Ledger Cluster CRD to expose the managed NATS sink and ownership-status schema, with periodic rediscovery after CRD upgrades
• report Ledger v3 ready only after the Cluster publishes a current SinksSynced=True condition; preserve legacy readiness for unmanaged Clusters

Validation

• nix develop --command just pre-commit
• nix develop --command just tests (17 suites; controller suite 139/139)
• focused Ledger controller integration suite (19/19)
• GitNexus change impact: CRITICAL, reviewed across 25 affected flows

Dependency

Depends on formancehq/ledger#1844 at 704e2741916104c1447ca1ae302c79a903788d9d.

[NumaryBot]

✅ Approve — automated review

No actionable defects were found in the current diff. Previously reported issues remain fixed at HEAD.

No findings.

[NumaryBot]

NumaryBot posted 2 new inline findings.

Summary: #530 (comment)

[NumaryBot]

NumaryBot posted 1 new inline finding.

Summary: #530 (comment)

[NumaryBot]

NumaryBot review complete: no remaining inline findings.

Resolved 1 stale NumaryBot review thread (0 fixed, 1 outdated).

Summary: #530 (comment)