Add a collapsible Markdown cheat sheet to the prompt input

A short, native <details>/<summary> reference (no JS) next to the
hint text, listing the basic syntax the new markdown rendering
supports: headings, bold/italic, lists, quotes, inline code, code
blocks, links.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/templates/prompts.html

@@ -40,6 +40,21 @@
         </div>
         <div class="muted" style="font-size:.8rem; margin-top:6px;">
           Der Prompt wird automatisch kategorisiert und mit Tags versehen.
+          Der Text unterstützt Markdown.
+          <details class="md-help">
+            <summary>{{ icons.sparkles(size=12) }} Markdown-Hilfe</summary>
+            <table>
+              <tr><td><code># Text</code></td><td>Überschrift</td></tr>
+              <tr><td><code>**Text**</code></td><td><strong>fett</strong></td></tr>
+              <tr><td><code>*Text*</code></td><td><em>kursiv</em></td></tr>
+              <tr><td><code>- Text</code></td><td>Aufzählung</td></tr>
+              <tr><td><code>1. Text</code></td><td>nummerierte Liste</td></tr>
+              <tr><td><code>&gt; Text</code></td><td>Zitat</td></tr>
+              <tr><td><code>`Text`</code></td><td><code>Inline-Code</code></td></tr>
+              <tr><td><code>```</code></td><td>Codeblock (davor &amp; danach)</td></tr>
+              <tr><td><code>[Text](url)</code></td><td>Link</td></tr>
+            </table>
+          </details>
         </div>
       </form>
     </div>