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/cypress.config.js

@@ -0,0 +1,13 @@
+import { defineConfig } from 'cypress'
+
+export default defineConfig({
+  e2e: {
+    baseUrl: 'http://localhost:5173',
+    supportFile: 'cypress/support/e2e.js',
+    specPattern: 'cypress/e2e/**/*.cy.{js,ts}',
+    viewportWidth: 1280,
+    viewportHeight: 800,
+    video: true,
+    videoCompression: false,
+  },
+})