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>

.gitea/workflows/preview.yml

@@ -0,0 +1,50 @@
+name: PR Preview
+on:
+  pull_request:
+    types: [opened, synchronize, reopened, closed]
+
+jobs:
+  test:
+    if: github.event.action != 'closed'
+    runs-on: test
+    steps:
+      - uses: actions/checkout@v4
+      - name: Build check
+        run: cd frontend && npm ci && npm run build
+
+  deploy-preview:
+    if: github.event.action != 'closed'
+    needs: test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Deploy Preview
+        run: python3 scripts/deploy-preview.py deploy ${{ github.event.pull_request.number }}
+      - name: Comment PR
+        env:
+          GIT_TOKEN: ${{ secrets.GIT_TOKEN }}
+        run: |
+          PR_ID="${{ github.event.pull_request.number }}"
+          curl -sf -X POST \
+            "https://git.euphon.cloud/api/v1/repos/${{ github.repository }}/issues/${PR_ID}/comments" \
+            -H "Authorization: token ${GIT_TOKEN}" \
+            -H "Content-Type: application/json" \
+            -d "{\"body\": \"🚀 **Preview**: https://pr-${PR_ID}.planner.oci.euphon.net\n\nDB is a copy of production.\"}" || true
+
+  teardown-preview:
+    if: github.event.action == 'closed'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Teardown
+        run: python3 scripts/deploy-preview.py teardown ${{ github.event.pull_request.number }}
+      - name: Comment PR
+        env:
+          GIT_TOKEN: ${{ secrets.GIT_TOKEN }}
+        run: |
+          PR_ID="${{ github.event.pull_request.number }}"
+          curl -sf -X POST \
+            "https://git.euphon.cloud/api/v1/repos/${{ github.repository }}/issues/${PR_ID}/comments" \
+            -H "Authorization: token ${GIT_TOKEN}" \
+            -H "Content-Type: application/json" \
+            -d "{\"body\": \"🗑️ Preview torn down.\"}" || true