Add visual and Markdown editors for ticket descriptions.

Replace the plain textarea with a dual-mode editor so ticket content can be written as WYSIWYG or Markdown while still storing Markdown.

Co-authored-by: Cursor <cursoragent@cursor.com>

web/src/App.svelte

@@ -2,6 +2,7 @@
   import { onMount } from 'svelte'
   import { api } from './lib/api.js'
   import { parseRoute, buildHash, currentHash } from './lib/route.js'
+  import MarkdownEditor from './lib/MarkdownEditor.svelte'
 
   let user = $state(null)
   let loading = $state(true)
@@ -888,7 +889,7 @@
                 <option value="done">DONE</option>
               </select>
             </label>
-            <label>Description<textarea bind:value={editDesc}></textarea></label>
+            <MarkdownEditor bind:value={editDesc} label="Description" />
             <button class="primary" onclick={saveTicket}>Save</button>
 
             <h3>Time</h3>