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/manifest.json

@@ -0,0 +1,11 @@
+{
+  "name": "Hera's Planner",
+  "short_name": "Planner",
+  "start_url": "/",
+  "display": "standalone",
+  "background_color": "#f0f2f5",
+  "theme_color": "#667eea",
+  "icons": [
+    { "src": "icon-180.png", "sizes": "180x180", "type": "image/png" }
+  ]
+}