feat: Nachrichten als wichtig markieren (Stern-Button)

- MessageRecord: neues Property IsMarked
- DatabaseService: Migration is_marked, ToggleMessageMark(), GetMarkedMessages()
- HistoryEndpoint: PUT /api/messages/{id}/mark (Toggle)
- SystemPromptBuilder: markierte Nachrichten als Referenz im System-Prompt
- ChatEndpoint + SessionEndpoint: markierte Nachrichten laden und an Builder übergeben
- Frontend: Stern-Button (☆/★) auf jeder Nachricht, Toggle per API
- CSS: .marked-Klasse mit gelbem Seitenrand, Button-Styling

wwwroot/js/api.js

@@ -131,6 +131,11 @@ async function apiGetChain(chainId) {
   return resp.json();
 }
 
+async function apiToggleMessageMark(messageId) {
+  const resp = await fetch(`/api/messages/${messageId}/mark`, { method: 'PUT' });
+  return resp.json();
+}
+
 async function apiGitStatus(sessionId) {
   const resp = await fetch(`/api/sessions/${sessionId}/git-status`);
   if (!resp.ok) return null;

wwwroot/js/history.js

@@ -35,11 +35,11 @@ function renderMessages(msgs, addToConversation) {
     switch (msg.type) {
       case 'text':
         if (msg.role === 'user') {
-          addUserBubble(msg.content, false, msg.createdAt);
+          addUserBubble(msg.content, false, msg.createdAt, msg.id, msg.isMarked);
           if (msg.attachmentCount > 0) addAttachmentIndicator(msg.id, msg.attachmentCount, msg.attachmentNames);
           if (addToConversation) messages.push({ role: 'user', content: msg.content });
         } else if (msg.role === 'assistant') {
-          addAssistantBubble(msg.content, msg.createdAt);
+          addAssistantBubble(msg.content, msg.createdAt, msg.id, msg.isMarked);
           if (addToConversation) messages.push({ role: 'assistant', content: msg.content });
         }
         break;

wwwroot/js/ui.js

@@ -33,6 +33,28 @@ function truncate(s, max) {
   return s && s.length > max ? s.substring(0, max) + '...' : (s || '');
 }
 
+// ── Mark Button ──
+
+function _addMarkButton(div, messageId, isMarked) {
+  if (!messageId) return; // kein DB-Eintrag → kein Button
+  const btn = document.createElement('button');
+  btn.className = 'msg-mark-btn icon-btn' + (isMarked ? ' marked' : '');
+  btn.innerHTML = isMarked ? '<i class="fa fa-star"></i>' : '<i class="fa fa-star-o"></i>';
+  btn.title = 'Als wichtig markieren';
+  btn.addEventListener('click', async (e) => {
+    e.stopPropagation();
+    try {
+      const result = await apiToggleMessageMark(messageId);
+      btn.classList.toggle('marked', result.isMarked);
+      btn.innerHTML = result.isMarked ? '<i class="fa fa-star"></i>' : '<i class="fa fa-star-o"></i>';
+      div.classList.toggle('marked', result.isMarked);
+    } catch (err) {
+      console.error('Mark toggle failed:', err);
+    }
+  });
+  div.prepend(btn);
+}
+
 // ── Reply Button ──
 
 function _addReplyButton(div) {
@@ -129,25 +151,29 @@ function _renderUserTextContent(container, raw) {
   container.appendChild(frag);
 }
 
-function addUserBubble(text, streamed = false, timestamp = '') {
+function addUserBubble(text, streamed = false, timestamp = '', messageId = null, isMarked = false) {
   const div = document.createElement('div');
-  div.className = 'msg user';
+  div.className = 'msg user' + (isMarked ? ' marked' : '');
   div.dataset.role = 'user';
   div.dataset.timestamp = timestamp || new Date().toISOString();
+  if (messageId) div.dataset.messageId = messageId;
   if (streamed) div.classList.add('streamed');
   renderUserContent(div, text);
   _addReplyButton(div);
+  _addMarkButton(div, messageId, isMarked);
   chatEl().appendChild(div);
   scrollDown();
 }
 
-function addAssistantBubble(text, timestamp = '') {
+function addAssistantBubble(text, timestamp = '', messageId = null, isMarked = false) {
   const div = document.createElement('div');
-  div.className = 'msg assistant markdown';
+  div.className = 'msg assistant markdown' + (isMarked ? ' marked' : '');
   div.dataset.role = 'assistant';
   div.dataset.timestamp = timestamp || new Date().toISOString();
+  if (messageId) div.dataset.messageId = messageId;
   div.innerHTML = renderMarkdown(text);
   _addReplyButton(div);
+  _addMarkButton(div, messageId, isMarked);
   chatEl().appendChild(div);
   scrollDown();
   return div;