style(journal): monochrome calendar icon instead of the emoji in day titles

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/features/workspace/DocumentEditor.tsx

@@ -24,6 +24,7 @@ import {
   Undo2,
   Redo2,
   MoreHorizontal,
+  CalendarDays,
 } from 'lucide-react';
 import { Document, DocumentBlock, User } from '../../lib/types';
 import { api } from '../../lib/api';
@@ -1265,10 +1266,17 @@ export const DocumentEditor: React.FC<DocumentEditorProps> = ({
                 <button
                   type="button"
                   onClick={() => canEdit && !inJournal && setShowEmojiPicker((prev) => !prev)}
-                  className="text-2xl sm:text-3xl hover:opacity-80 transition-opacity cursor-pointer select-none leading-none bg-transparent border-0 outline-none p-0 focus:outline-none focus:ring-0 shadow-none"
-                  title="Icon ändern"
+                  className={`text-2xl sm:text-3xl transition-opacity select-none leading-none bg-transparent border-0 outline-none p-0 focus:outline-none focus:ring-0 shadow-none ${
+                    inJournal ? 'cursor-default' : 'hover:opacity-80 cursor-pointer'
+                  }`}
+                  title={inJournal ? undefined : 'Icon ändern'}
                 >
-                  {doc?.icon || '📝'}
+                  {/* Journal days: a quiet calendar in the theme's text colour instead of the colourful emoji */}
+                  {inJournal ? (
+                    <CalendarDays className="w-6 h-6 sm:w-7 sm:h-7 text-muted" strokeWidth={1.75} />
+                  ) : (
+                    doc?.icon || '📝'
+                  )}
                 </button>
                 {showEmojiPicker && canEdit && (
                   <EmojiPickerModal