DM inbox caching and linkification improvements (v0.2.4)

- Add MessageContent component for linkified DM messages
- URLs open in new tab, nostr: entities open in secondary pane
- Implement background refresh that merges instead of clearing cache
- Show cached conversations immediately on page load
- Fix navigation not reloading conversations unnecessarily

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

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

package.json

@@ -1,6 +1,6 @@
 {
   "name": "smesh",
-  "version": "0.2.2",
+  "version": "0.2.4",
   "description": "A user-friendly Nostr client for exploring relay feeds",
   "private": true,
   "type": "module",