docs: add v1.0.9 CHANGELOG entry

Documents everything since the v1.0.8 entry: icon batches, the Web
Applications active-app info card, PWA support, Log Entries filters
and refresh button, Accounts list columns, the account-switch fixes
(reviewed against and aligned with upstream's own fix for the same
issue), the WebUI Fork rename, mailbox hierarchy, new color themes,
and the confirmed-backend-only limitations (Log filter properties,
exact-match-only text search across the admin API).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

package.json

@@ -1,7 +1,7 @@
 {
   "name": "stalwart-webui-fork",
   "private": true,
-  "version": "1.0.8",
+  "version": "1.0.9",
   "description": "Stalwart WebUI Fork",
   "type": "module",
   "scripts": {