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/favorites.cy.js

@@ -0,0 +1,87 @@
+describe('Favorites System', () => {
+  const ADMIN_TOKEN = 'c86ae7afbe10fabe3c1d5e1a7fee74feaadfd5dc7be2ab62'
+
+  describe('API Level', () => {
+    let firstRecipeId
+
+    before(() => {
+      cy.request('/api/recipes').then(res => {
+        firstRecipeId = res.body[0].id
+      })
+    })
+
+    it('can add a favorite via API', () => {
+      cy.request({
+        method: 'POST',
+        url: `/api/favorites/${firstRecipeId}`,
+        headers: { Authorization: `Bearer ${ADMIN_TOKEN}` },
+        body: {}
+      }).then(res => {
+        expect(res.status).to.be.oneOf([200, 201])
+      })
+    })
+
+    it('lists the favorite', () => {
+      cy.request({
+        url: '/api/favorites',
+        headers: { Authorization: `Bearer ${ADMIN_TOKEN}` }
+      }).then(res => {
+        expect(res.body).to.include(firstRecipeId)
+      })
+    })
+
+    it('can remove the favorite via API', () => {
+      cy.request({
+        method: 'DELETE',
+        url: `/api/favorites/${firstRecipeId}`,
+        headers: { Authorization: `Bearer ${ADMIN_TOKEN}` }
+      }).then(res => {
+        expect(res.status).to.eq(200)
+      })
+    })
+
+    it('favorite is removed from list', () => {
+      cy.request({
+        url: '/api/favorites',
+        headers: { Authorization: `Bearer ${ADMIN_TOKEN}` }
+      }).then(res => {
+        expect(res.body).to.not.include(firstRecipeId)
+      })
+    })
+  })
+
+  describe('UI Level', () => {
+    it('recipe cards have star buttons for logged-in users', () => {
+      cy.visit('/', {
+        onBeforeLoad(win) {
+          win.localStorage.setItem('oil_auth_token', ADMIN_TOKEN)
+        }
+      })
+      cy.get('.recipe-card', { timeout: 10000 }).should('have.length.gte', 1)
+      // Stars should be present on cards
+      cy.get('.recipe-card').first().within(() => {
+        cy.contains(/★|☆/).should('exist')
+      })
+    })
+
+    it('clicking star toggles favorite state', () => {
+      cy.visit('/', {
+        onBeforeLoad(win) {
+          win.localStorage.setItem('oil_auth_token', ADMIN_TOKEN)
+        }
+      })
+      cy.get('.recipe-card', { timeout: 10000 }).first().within(() => {
+        cy.contains(/★|☆/).then($star => {
+          const wasFav = $star.text().includes('★')
+          $star.trigger('click')
+          // Star text should have toggled
+          cy.wait(500)
+          cy.contains(/★|☆/).invoke('text').should(text => {
+            if (wasFav) expect(text).to.include('☆')
+            else expect(text).to.include('★')
+          })
+        })
+      })
+    })
+  })
+})