feat!: update Dart SDK minimum versions

BREAKING CHANGE: Minimum Dart SDK version updated
- cherrypick_annotations: 3.8.0 -> 3.9.0
- cherrypick_generator: requires Dart 3.9.0+

This change may require users to update their Dart SDK.

CHANGELOG.md

@@ -3,6 +3,28 @@
 All notable changes to this project will be documented in this file.
 See [Conventional Commits](https://conventionalcommits.org) for commit guidelines.
 
+## 2026-01-29
+
+### Changes
+
+---
+
+Packages with breaking changes:
+
+ - There are no breaking changes in this release.
+
+Packages with other changes:
+
+ - [`cherrypick_annotations` - `v3.0.3`](#cherrypick_annotations---v303)
+ - [`cherrypick_generator` - `v3.0.3`](#cherrypick_generator---v303)
+
+---
+
+#### `cherrypick_annotations` - `v3.0.3`
+
+#### `cherrypick_generator` - `v3.0.3`
+
+
 ## 2026-01-29
 
 ### Changes