feat(update): notify about app updates on launch (chat banner) (#891)

Fires one silent update check per installed version at app start
(UpdateNoticeManager, release builds only) and shows a non-blocking
banner on the chat screen when a newer release exists. The About tab
adopts the launch result instead of re-pinging GitHub; dismissals
return on the next launch via the persisted latest tag.

Closes #890

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/res/values/strings.xml

@@ -983,6 +983,10 @@
     <string name="action_done">Done</string>
     <string name="action_close">Close</string>
 
+    <!-- Update notice banner (issue #890) -->
+    <string name="update_notice_banner_text">Hermes Mobile %1$s is available</string>
+    <string name="update_notice_banner_action">Update</string>
+
     <!-- Processes Screen (issue #532) -->
     <string name="processes_empty_title">No running processes</string>
     <string name="processes_empty_desc">Background processes for this session will appear here.</string>