Add image preview support: Krea-tag parsing with modal, file-explorer preview, skill output endpoint, increase execute timeout to 180s

- SkillEndpoint: GET /api/skills/{slug}/output/{filename} for skill output files
- WorkspaceEndpoint: GET /api/workspace/raw for raw file serving (images)
- File-Explorer: Image preview for png/jpg/gif/webp/svg/bmp/ico
- Chat UI: Parse [Krea: filename] tags into clickable chips with image modal
- ToolService: Increase execute timeout from 30s to 180s for long-running skills

wwwroot/js/file-explorer.js

@@ -204,6 +204,15 @@ async function feSelectFile(entry, itemEl) {
   // Vorherige Editor-Instanz aufräumen
   feDestroyEditor();
 
+  const imageExts = ['.png', '.jpg', '.jpeg', '.gif', '.webp', '.svg', '.bmp', '.ico'];
+  if (!entry.isText && imageExts.includes((entry.ext || '').toLowerCase())) {
+    const rawUrl = _feApiUrl('raw', `path=${encodeURIComponent(entry.path)}`);
+    main.innerHTML = `<div class="fe-image-preview"><img src="${rawUrl}" alt="${esc(entry.name)}" /></div>`;
+    footer.hidden = true;
+    _feState.selectedFile = null;
+    return;
+  }
+
   if (!entry.isText) {
     main.innerHTML = `<div class="fe-placeholder">${getFileIcon(entry.ext)} ${esc(entry.name)}<br><small>${formatSize(entry.size)} - Vorschau nicht verfügbar</small></div>`;
     footer.hidden = true;