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/src/composables/useApi.js

@@ -0,0 +1,44 @@
+const API_BASE = ''  // same origin, uses vite proxy in dev
+
+export function getToken() {
+  return localStorage.getItem('oil_auth_token') || ''
+}
+
+export function setToken(token) {
+  if (token) localStorage.setItem('oil_auth_token', token)
+  else localStorage.removeItem('oil_auth_token')
+}
+
+function buildHeaders(extra = {}) {
+  const headers = { 'Content-Type': 'application/json', ...extra }
+  const token = getToken()
+  if (token) headers['Authorization'] = 'Bearer ' + token
+  return headers
+}
+
+async function request(path, opts = {}) {
+  const headers = buildHeaders(opts.headers)
+  const res = await fetch(API_BASE + path, { ...opts, headers })
+  return res
+}
+
+async function requestJSON(path, opts = {}) {
+  const res = await request(path, opts)
+  if (!res.ok) throw res
+  return res.json()
+}
+
+// api is callable as api(path, opts) → raw Response
+// AND has convenience methods: api.get(), api.post(), api.put(), api.delete()
+function apiFn(path, opts = {}) {
+  return request(path, opts)
+}
+
+apiFn.raw = request
+apiFn.get = (path) => requestJSON(path)
+apiFn.post = (path, body) => requestJSON(path, { method: 'POST', body: JSON.stringify(body) })
+apiFn.put = (path, body) => requestJSON(path, { method: 'PUT', body: JSON.stringify(body) })
+apiFn.del = (path) => requestJSON(path, { method: 'DELETE' })
+apiFn.delete = (path) => requestJSON(path, { method: 'DELETE' })
+
+export const api = apiFn