Refactor to Vue 3 + FastAPI + SQLite architecture

- Backend: FastAPI + SQLite (WAL mode), 22 tables, ~40 API endpoints
- Frontend: Vue 3 + Vite + Pinia + Vue Router, 8 views, 3 stores
- Database: migrate from JSON file to SQLite with proper schema
- Dockerfile: multi-stage build (node + python)
- Deploy: K8s manifests (namespace, deployment, service, ingress, pvc, backup)
- CI/CD: Gitea Actions (test, deploy, PR preview at pr-$id.planner.oci.euphon.net)
- Tests: 20 Cypress E2E test files, 196 test cases, ~85% coverage
- Doc: test-coverage.md with full feature coverage report

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/public/sw.js

@@ -0,0 +1,25 @@
+// Service Worker for Hera's Planner — 后台提醒通知
+self.addEventListener('install', () => self.skipWaiting());
+self.addEventListener('activate', () => self.clients.claim());
+
+self.addEventListener('message', event => {
+  if (event.data && event.data.type === 'SHOW_NOTIFICATION') {
+    self.registration.showNotification(event.data.title, {
+      body: event.data.body,
+      icon: 'icon-180.png',
+      badge: 'icon-180.png',
+      requireInteraction: true,
+      tag: event.data.tag || 'planner-reminder',
+    });
+  }
+});
+
+self.addEventListener('notificationclick', event => {
+  event.notification.close();
+  event.waitUntil(
+    self.clients.matchAll({ type: 'window' }).then(clients => {
+      if (clients.length > 0) { clients[0].focus(); }
+      else { self.clients.openWindow('/'); }
+    })
+  );
+});