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/e2e/performance.cy.js

@@ -0,0 +1,58 @@
+describe('Performance', () => {
+  it('home page loads within 5 seconds', () => {
+    const start = Date.now()
+    cy.visit('/')
+    cy.get('.recipe-card', { timeout: 5000 }).should('have.length.gte', 1)
+    cy.then(() => {
+      const elapsed = Date.now() - start
+      expect(elapsed).to.be.lt(5000)
+    })
+  })
+
+  it('API /api/oils responds within 1 second', () => {
+    const start = Date.now()
+    cy.request('/api/oils').then(() => {
+      expect(Date.now() - start).to.be.lt(1000)
+    })
+  })
+
+  it('API /api/recipes responds within 2 seconds', () => {
+    const start = Date.now()
+    cy.request('/api/recipes').then(() => {
+      expect(Date.now() - start).to.be.lt(2000)
+    })
+  })
+
+  it('search filtering is near-instant', () => {
+    cy.visit('/')
+    cy.get('.recipe-card', { timeout: 10000 }).should('have.length.gte', 1)
+    const start = Date.now()
+    cy.get('input[placeholder*="搜索"]').type('薰衣草')
+    cy.wait(300)
+    cy.get('.recipe-card').should('exist')
+    cy.then(() => {
+      expect(Date.now() - start).to.be.lt(2000)
+    })
+  })
+
+  it('oil reference page loads within 3 seconds', () => {
+    const start = Date.now()
+    cy.visit('/oils')
+    cy.get('.oil-card', { timeout: 3000 }).should('have.length.gte', 1)
+    cy.then(() => {
+      expect(Date.now() - start).to.be.lt(3000)
+    })
+  })
+
+  it('handles 250+ recipes without crashing', () => {
+    cy.request('/api/recipes').then(res => {
+      expect(res.body.length).to.be.gte(200)
+    })
+    cy.visit('/')
+    cy.get('.recipe-card', { timeout: 10000 }).should('have.length.gte', 10)
+    // Scroll to trigger lazy loading if any
+    cy.scrollTo('bottom')
+    cy.wait(500)
+    cy.get('.main').should('be.visible')
+  })
+})