feat(favorites): keep customer favourites on the server, as legacy did (FAV-01)

Both apps kept favourites in memory only, and the API had no route, so
the 874 favourites imported from legacy major_favorites never showed.

- GET customer/me/favorites, POST customer/me/favorites/toggle
- apps load them on sign-in, clear on sign-out, toggle optimistically
  and roll back on failure

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/user-app/src/api/client.ts

@@ -336,6 +336,14 @@ export const api = {
   getAccountingBalance: () => request<AccountingBalance>('/customer/me/accounting-balance'),
   getMyOrders: () => request<OrderDetail[]>('/customer/me/orders'),
   getMyLedgerEntries: () => request<LedgerEntrySummary[]>('/customer/me/ledger-entries'),
+  /** Favourite product ids, newest first — legacy get-favorites (FAV-01). */
+  getFavorites: () => request<{ ids: string[] }>('/customer/me/favorites'),
+  /** Legacy add-to-fav: adds or removes; answers the new state. */
+  toggleFavorite: (productId: string) =>
+    request<{ favorite: boolean }>('/customer/me/favorites/toggle', {
+      method: 'POST',
+      body: JSON.stringify({ productId }),
+    }),
 
   createOrder: (dto: CreateOrderDto) => request<OrderSummary>('/orders', { method: 'POST', body: JSON.stringify(dto) }),
   getLatestGoldPrice: (karatPerMille = 750) => request<GoldPriceQuote>(`/pricing/latest?karatPerMille=${karatPerMille}`),

apps/user-app/src/stores/favoritesStore.ts

@@ -1,22 +1,55 @@
 // Adapted from legacy henza_pwa/src/Mixins/favorite.ts + the `favorits` slice of
-// myDataStore. Legacy persisted favorites server-side via POST /add-to-fav; the
-// new API has no favorites endpoint yet, so this is local-only (Pinia state,
-// not persisted) until that backend support exists. Flagged — not a silent
-// behavior match, a deliberate stand-in.
+// myDataStore. Legacy kept favourites on the server (POST add-to-fav /
+// get-favorites, table major_favorites); so does this, through
+// /customer/me/favorites (FAV-01). It used to be memory-only, so favourites
+// vanished on reload and the ones imported from legacy were never shown.
 import { defineStore } from 'pinia'
+import { ref, watch } from 'vue'
+import { api } from '../api/client'
+import { useSessionStore } from './session'
 
-export const useFavoritesStore = defineStore('favorites', {
-  state: () => ({
-    ids: [] as string[],
-  }),
-  actions: {
-    toggle(id: string) {
-      const index = this.ids.indexOf(id)
-      if (index === -1) this.ids.push(id)
-      else this.ids.splice(index, 1)
+export const useFavoritesStore = defineStore('favorites', () => {
+  const ids = ref<string[]>([])
+  const session = useSessionStore()
+
+  async function load() {
+    try {
+      ids.value = (await api.getFavorites()).ids
+    } catch (e) {
+      // Offline or a dead session (the client already handles 401): keep what we have.
+      console.warn('favorites: load failed', e)
+    }
+  }
+
+  // Loaded for whoever is signed in, cleared on logout — never another user's list.
+  watch(
+    () => session.token,
+    (token) => {
+      ids.value = []
+      if (token) void load()
     },
-    isFavorite(id: string) {
-      return this.ids.includes(id)
-    },
-  },
+    { immediate: true },
+  )
+
+  /** Flips at once on screen, then confirms with the server (legacy toggled the same way). */
+  async function toggle(id: string) {
+    const was = ids.value.includes(id)
+    ids.value = was ? ids.value.filter((x) => x !== id) : [id, ...ids.value]
+    try {
+      const { favorite } = await api.toggleFavorite(id)
+      const has = ids.value.includes(id)
+      if (favorite && !has) ids.value = [id, ...ids.value]
+      if (!favorite && has) ids.value = ids.value.filter((x) => x !== id)
+    } catch (e) {
+      // Put it back so the heart never shows a state the server does not hold.
+      ids.value = was ? [id, ...ids.value.filter((x) => x !== id)] : ids.value.filter((x) => x !== id)
+      console.warn('favorites: toggle failed', e)
+    }
+  }
+
+  function isFavorite(id: string) {
+    return ids.value.includes(id)
+  }
+
+  return { ids, load, toggle, isFavorite }
 })