doc: Add comment about similar code.

src/components/DataExportSection.vue

@@ -168,6 +168,8 @@ export default class DataExportSection extends Vue {
    * @throws {Error} If export fails
    */
   public async exportDatabase(): Promise<void> {
+    // Note that similar code is in ContactsView.vue exportContactData()
+
     if (this.isExporting) {
       return; // Prevent multiple simultaneous exports
     }

src/views/ContactsView.vue

@@ -1296,6 +1296,7 @@ export default class ContactsView extends Vue {
    * Uses platform service to handle platform-specific export logic
    */
   private async exportContactData(): Promise<void> {
+    // Note that similar code is in DataExportSection.vue exportDatabase()
     try {
       // Fetch all contacts from database
       const allContacts = await this.$contacts();