Fix critical bugs: oil prices ¥0.00, ingredient field mapping

- oils store: change Map to plain object for Vue reactivity
- recipes store: map `oil_name` from API (was only mapping `oil`/`name`)
- OilReference: fix .get() calls to bracket access
- Add price-display.cy.js regression test (3 tests)
- Add visual-check.cy.js for screenshot verification

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

frontend/cypress/e2e/price-display.cy.js

@@ -0,0 +1,39 @@
+describe('Price Display Regression', () => {
+  it('recipe cards show non-zero prices', () => {
+    cy.visit('/')
+    cy.get('.recipe-card', { timeout: 10000 }).should('have.length.gte', 1)
+    cy.wait(2000) // wait for oils store to load and re-render
+
+    // Check via .card-price elements which hold the formatted cost
+    cy.get('.card-price').first().invoke('text').then(text => {
+      const match = text.match(/¥\s*(\d+\.?\d*)/)
+      expect(match, 'Card price should contain ¥').to.not.be.null
+      expect(parseFloat(match[1]), 'Price should be > 0').to.be.gt(0)
+    })
+  })
+
+  it('oil reference page shows non-zero prices', () => {
+    cy.visit('/oils')
+    cy.get('.oil-card', { timeout: 10000 }).should('have.length.gte', 1)
+    cy.wait(500)
+
+    cy.get('.oil-card').first().invoke('text').then(text => {
+      const match = text.match(/¥\s*(\d+\.?\d*)/)
+      expect(match, 'Oil card should contain a price').to.not.be.null
+      expect(parseFloat(match[1])).to.be.gt(0)
+    })
+  })
+
+  it('recipe detail shows non-zero total cost', () => {
+    cy.visit('/')
+    cy.get('.recipe-card', { timeout: 10000 }).first().click()
+    cy.wait(1000)
+
+    // Look for any ¥ amount > 0 in the detail overlay
+    cy.get('[class*="overlay"], [class*="detail"]').invoke('text').then(text => {
+      const prices = [...text.matchAll(/¥\s*(\d+\.?\d*)/g)].map(m => parseFloat(m[1]))
+      const nonZero = prices.filter(p => p > 0)
+      expect(nonZero.length, 'Detail should show at least one non-zero price').to.be.gte(1)
+    })
+  })
+})