chore(release): v0.2.1

Bump root, backend, and frontend to 0.2.1 and add the 0.2.1 changelog section.
Patch release: pagination styling, patient-sheet header reflow, message
avatars, and CHANGELOG-based GitHub Release notes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "frontend",
-  "version": "0.2.0",
+  "version": "0.2.1",
   "private": true,
   "scripts": {
     "dev": "next dev",