Fix disabled save button styling in dark mode

- Changed disabled save button background from light grey to dark grey in dark mode
- Changed disabled save button text from grey-400 to grey-500 in dark mode
- Button now blends better with dark mode design
- No longer draws unwanted attention when disabled

src/components/NoteEditor.tsx

@@ -159,7 +159,7 @@ export function NoteEditor({ note, onUpdateNote, fontSize }: NoteEditorProps) {
             className={`p-2 rounded-lg transition-colors ${
               hasUnsavedChanges && !isSaving
                 ? 'bg-blue-500 text-white hover:bg-blue-600'
-                : 'bg-gray-200 text-gray-400 cursor-not-allowed'
+                : 'bg-gray-200 dark:bg-gray-700 text-gray-400 dark:text-gray-500 cursor-not-allowed'
             }`}
             title="Save Note"
           >