fix: update release-please to use prerelease versioning

- Change versioning strategy from always-bump-patch to prerelease
- Set version to 5.0.0-alpha.21.1

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: dbrattli

.release-please-manifest.json

@@ -1,3 +1,3 @@
 {
-  ".": "5.0.0-alpha.21.0"
+  ".": "5.0.0-alpha.21.1"
 }

release-please-config.json

@@ -3,7 +3,7 @@
   "packages": {
     ".": {
       "release-type": "simple",
-      "versioning": "always-bump-patch",
+      "versioning": "prerelease",
       "include-component-in-tag": false,
       "include-v-in-tag": true,
       "changelog-path": "CHANGELOG.md"