chore: bump version to 0.5.0 for release

- Update version in root, opencode-plugin, and server packages
- Add code review feature to README
- Build artifacts for release

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/server/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@plannotator/server",
-  "version": "0.4.16",
+  "version": "0.5.0",
   "private": true,
   "description": "Shared server implementation for Plannotator plugins",
   "main": "index.ts",