feat: Vollbild-Modus für Chat-Assistent

Neuer Button zwischen Reload und Schließen. Toggled zwischen
normalem Fenster und Vollbild. Icon wechselt zwischen Expand/Collapse.
Schließen und Reset beenden Vollbild automatisch.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/static/js/chat.js

@@ -6,6 +6,7 @@ const Chat = {
     _isOpen: false,
     _isLoading: false,
     _hasGreeted: false,
+    _isFullscreen: false,
 
     init() {
         const btn = document.getElementById('chat-toggle-btn');
@@ -21,6 +22,9 @@ const Chat = {
         const resetBtn = document.getElementById('chat-reset-btn');
         if (resetBtn) resetBtn.addEventListener('click', () => this.reset());
 
+        const fsBtn = document.getElementById('chat-fullscreen-btn');
+        if (fsBtn) fsBtn.addEventListener('click', () => this.toggleFullscreen());
+
         form.addEventListener('submit', (e) => {
             e.preventDefault();
             this.send();
@@ -74,8 +78,15 @@ const Chat = {
         const btn = document.getElementById('chat-toggle-btn');
         if (!win) return;
         win.classList.remove('open');
+        win.classList.remove('fullscreen');
         btn.classList.remove('active');
         this._isOpen = false;
+        this._isFullscreen = false;
+        const fsBtn = document.getElementById('chat-fullscreen-btn');
+        if (fsBtn) {
+            fsBtn.title = 'Vollbild';
+            fsBtn.innerHTML = '<svg viewBox="0 0 24 24" width="15" height="15"><path d="M7 14H5v5h5v-2H7v-3zm-2-4h2V7h3V5H5v5zm12 7h-3v2h5v-5h-2v3zM14 5v2h3v3h2V5h-5z" fill="currentColor"/></svg>';
+        }
     },
 
     reset() {
@@ -88,6 +99,20 @@ const Chat = {
         this.open();
     },
 
+    toggleFullscreen() {
+        const win = document.getElementById('chat-window');
+        const btn = document.getElementById('chat-fullscreen-btn');
+        if (!win) return;
+        this._isFullscreen = !this._isFullscreen;
+        win.classList.toggle('fullscreen', this._isFullscreen);
+        if (btn) {
+            btn.title = this._isFullscreen ? 'Vollbild beenden' : 'Vollbild';
+            btn.innerHTML = this._isFullscreen
+                ? '<svg viewBox="0 0 24 24" width="15" height="15"><path d="M5 16h3v3h2v-5H5v2zm3-8H5v2h5V5H8v3zm6 11h2v-3h3v-2h-5v5zm2-11V5h-2v5h5V8h-3z" fill="currentColor"/></svg>'
+                : '<svg viewBox="0 0 24 24" width="15" height="15"><path d="M7 14H5v5h5v-2H7v-3zm-2-4h2V7h3V5H5v5zm12 7h-3v2h5v-5h-2v3zM14 5v2h3v3h2V5h-5z" fill="currentColor"/></svg>';
+        }
+    },
+
     _updateResetBtn() {
         const btn = document.getElementById('chat-reset-btn');
         if (btn) btn.style.display = this._conversationId ? '' : 'none';