Add release notes 16.6.6

Author: oliverguenther

docs/release-notes/16-6-6/README.md

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+---
+title: OpenProject 16.6.6
+sidebar_navigation:
+    title: 16.6.6
+release_version: 16.6.6
+release_date: 2026-01-27
+---
+
+# OpenProject 16.6.6
+
+Release date: 2026-01-27
+
+We released OpenProject [OpenProject 16.6.6](https://community.openproject.org/versions/2261).
+The release contains security related bug fixes and we strongly urge you to update to the newest version.
+Below you will find a complete list of all changes and bug fixes.
+
+<!--more-->
+
+## Bug fixes and changes
+
+<!-- Warning: Anything within the below lines will be automatically removed by the release script -->
+<!-- BEGIN AUTOMATED SECTION -->
+
+- Bugfix: Fix revision parsing in git diff output \[[#71019](https://community.openproject.org/wp/71019)\]
+
+<!-- END AUTOMATED SECTION -->
+<!-- Warning: Anything above this line will be automatically removed by the release script -->