Update CHANGELOG.md for v1.0.3 release

Author: vnykmshr

CHANGELOG.md

@@ -2,6 +2,30 @@
 
 All notable changes to this project will be documented in this file.
 
+## [1.0.3] - 2025-09-16
+
+### Code Quality & Production Readiness
+
+**Improvements:**
+- Pre-production code cleanup and standardization
+- Remove development artifacts (12MB binary cleanup)
+- Consolidate test constants into centralized `testutil.go`
+- Standardize code formatting across all example files
+- Fix unused imports and resolve all lint issues
+- Improve struct field alignment and code consistency
+
+**Technical Enhancements:**
+- Add centralized test constants: `TestTTL`, `TestSlowOperation`, `TestMetricsReportInterval`
+- Standardize time duration usage in tests and examples
+- Clean dependency management and `go.sum` optimization
+- Ensure consistent indentation and professional code style
+
+**Quality Assurance:**
+- All tests pass with clean build pipeline
+- Production-ready codebase with improved maintainability
+- Code now reads as unified, professionally developed library
+- Ready for enterprise deployment
+
 ## [1.0.0] - 2025-08-27
 
 ### Initial Release