Add metrics instrumentation after data sync and persistence are implemented

[coderabbitai]

Overview

Add comprehensive metrics instrumentation to the peer-session layer and related components once data sync and persistence have been implemented.

Context

The peer-session package (introduced in #29) creates TransportLibp2p instances that already wire up createTransportMetrics(), but full metrics integration (e.g. initialising a global MeterProvider via initMetrics) is deferred until the data layer is more stable.

Tasks

• Identify and instrument key operations in the peer-session layer (relay startup, node startup, peer discovery, messaging)
• Add metrics coverage for data sync operations once implemented
• Add initMetrics / shutdownMetrics hooks to the integration test suite (packages/peer-session/tests/transport-libp2p/integration.test.ts)
• Ensure all instrumented components bind to a real MeterProvider rather than the no-op meter

References

• PR: Feat/add developer cli app #29
• Review comment: Feat/add developer cli app #29 (comment)

/cc @jost-s