docs: update README and changelog for OTEL

Align documentation and changelog entries with the OTEL integration
behavior and references.

Author: artem-tkachuk

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- [#1062](https://github.com/spegel-org/spegel/pull/1062) Add OpenTelemetry tracing support with OTEL configuration (endpoint, insecure, serviceName, sampler) and trace correlation (trace_id/span_id) in structured logs.
 - [#1056](https://github.com/spegel-org/spegel/pull/1056) Send delete events for content by keeping content index.
 
 ### Changed

README.md

@@ -19,6 +19,7 @@ Spegel is for you if you are looking to do any of the following.
 * Avoid rate-limiting when pulling images from external registries (e.g. Docker Hub).
 * Decrease egressing traffic outside of the clusters network.
 * Increase image pull efficiency in edge node deployments.
+* OpenTelemetry tracing.
 
 ## Getting Started