chore: bump version to 0.4.9 and remove session switch transition overlay (#235)

- Remove isTransitioning overlay that caused white screen on session switch
- Simplify scroll logic: just scrollToBottom() on session change
- Remove changelog entry for removed transition feature

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "hermes-web-ui",
-  "version": "0.4.8",
+  "version": "0.4.9",
   "description": "Self-hosted AI chat dashboard for Hermes Agent — multi-model (Claude, GPT, Gemini, DeepSeek) web UI with Telegram, Discord, Slack, WhatsApp integration",
   "repository": {
     "type": "git",