feat: add message queue for sequential run processing (#501)

Allow sending multiple messages while a run is active. Messages are
queued on the server and processed sequentially after each run
completes. Each completed assistant message triggers speech playback
independently, and the UI shows queue status with a badge indicator.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

packages/client/src/i18n/locales/de.ts

@@ -117,6 +117,8 @@ export default {
     emptyState: 'Starten Sie eine Konversation mit Hermes Agent',
     inputPlaceholder: 'Nachricht eingeben... (Enter zum Senden, Shift+Enter fur neue Zeile)',
     attachFiles: 'Dateien anhangen',
+    messageQueue: 'Nachrichtenwarteschlange',
+    removeQueuedMessage: 'Nachricht aus Warteschlange entfernen',
     stop: 'Stopp',
     send: 'Senden',
     contextUsed: 'Kontext verwendet:',