chore: bump version to 0.3.1

CHANGELOG.md

@@ -5,6 +5,13 @@ All notable changes to fastapi-traffic will be documented here.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.3.1] - 2026-03-19
+
+### Changed
+
+- Updated documentation version references to match release version
+- Synchronized docs/changelog.rst with CHANGELOG.md
+
 ## [0.3.0] - 2026-03-17
 
 ### Added