docs: merge notification system docs into single Native-First guide

- Consolidate 5 notification-system-* files into doc/notification-system.md
- Add web-push cleanup guide and Start-on-Login glossary entry
- Configure markdownlint for consistent formatting
- Remove web-push references, focus on native OS scheduling

Reduces maintenance overhead while preserving all essential information
in a single, well-formatted reference document.

src/views/ContactQRScanFullView.vue

@@ -144,6 +144,7 @@ import {
   QR_TIMEOUT_LONG,
 } from "@/constants/notifications";
 import { createNotifyHelpers, NotifyFunction } from "../utils/notify";
+import { showSeedPhraseReminder } from "@/utils/seedPhraseReminder";
 
 interface QRScanResult {
   rawValue?: string;
@@ -627,6 +628,15 @@ export default class ContactQRScanFull extends Vue {
    */
   async handleBack() {
     await this.cleanupScanner();
+
+    // Show seed phrase backup reminder if needed
+    try {
+      const settings = await this.$accountSettings();
+      showSeedPhraseReminder(!!settings.hasBackedUpSeed, this.$notify);
+    } catch (error) {
+      logger.error("Error checking seed backup status:", error);
+    }
+
     this.$router.back();
   }