Dependency maintenance: consume Timing 2.2.3 and audit Event dependency direction

[LK-Simon]

Summary

Refresh ESP-Now's required Timing baseline after the Serializable 0.10.1 cascade and audit the existing optional Event relationship for circular dependency risk.

Scope

• Prepare ESPressio ESP-Now 0.5.1.
• Update required Timing references from 2.2.2 to 2.2.3 and current self-version documentation from 0.5.0 to 0.5.1.
• Update current optional dependency references where appropriate without introducing a reciprocal package dependency.
• Update CHANGELOG, dependency chart, examples/tests/workflows, and package metadata as applicable.
• Validate against Timing 2.2.3, Observable 3.0.1, and current optional integration baselines.

Circular-dependency audit

Today ESP-Now optionally consumes Event for Event transport, while Event 5.8 optionally consumes ESP-Now for ESPNowTransportEventBridge. That creates an optional architectural cycle.

Preferred long-term direction: Event remains upstream; ESP-Now owns downstream Event-specific integration (ESPNowEventTransport and the ESP-Now observer-to-Event bridge), or the integration moves to a dedicated downstream package. Event should not depend back on ESP-Now.

This maintenance release should document the issue but avoid a breaking bridge relocation.

Release order

Serializable 0.10.1 -> Units 0.2.2 -> Timing 2.2.3 -> ESP-Now 0.5.1.