History Polling: Message-ID-basiert, neuer /api/history/poll Endpoint

wwwroot/js/chat.js

@@ -1,6 +1,7 @@
 // ── Chat State ──
 
 const messages = [];
+let isStreaming = false;
 
 function clearChat() {
   messages.length = 0;
@@ -24,6 +25,7 @@ async function sendMessage() {
   input.value = '';
   input.style.height = 'auto';
   btn.disabled = true;
+  isStreaming = true;
   setMetaHtml('<span style="color:#7c83ff">⏳ Streaming...</span>');
 
   let fullText = '';
@@ -103,6 +105,7 @@ async function sendMessage() {
     addErrorBubble('Netzwerk-Fehler: ' + e.message);
   } finally {
     btn.disabled = false;
+    isStreaming = false;
     endStreamBubble();
   }
 }