Refactor frontend to Vue 3 + Vite + Pinia + Cypress E2E

- Replace single-file 8441-line HTML with Vue 3 SPA
- Pinia stores: auth, oils, recipes, diary, ui
- Composables: useApi, useDialog, useSmartPaste, useOilTranslation
- 6 shared components: RecipeCard, RecipeDetailOverlay, TagPicker, etc.
- 9 page views: RecipeSearch, RecipeManager, Inventory, OilReference, etc.
- 14 Cypress E2E test specs (113 tests), all passing
- Multi-stage Dockerfile (Node build + Python runtime)
- Demo video generation scripts (TTS + subtitles + screen recording)

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

frontend/package.json

@@ -0,0 +1,26 @@
+{
+  "name": "frontend",
+  "private": true,
+  "version": "0.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "vite build",
+    "preview": "vite preview",
+    "cy:open": "cypress open",
+    "cy:run": "cypress run",
+    "test:e2e": "cypress run"
+  },
+  "dependencies": {
+    "exceljs": "^4.4.0",
+    "html2canvas": "^1.4.1",
+    "pinia": "^2.3.1",
+    "vue": "^3.5.32",
+    "vue-router": "^4.6.4"
+  },
+  "devDependencies": {
+    "@vitejs/plugin-vue": "^6.0.5",
+    "cypress": "^15.13.0",
+    "vite": "^8.0.4"
+  }
+}