chore(release): finalize v1.1.0 release preparation

- Update CHANGELOG.md with release date 2026-02-21
- Add release-readiness gate documents (all gates PASS)

Author: MarketDataApp

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 ## [Unreleased]
 
-## v1.1.0 (Unreleased)
+## v1.1.0 (2026-02-21)
 
 ### Breaking Changes