refactor(data): add mock API adapters, id utility, and toast feedback

lib/api/favorites.ts

@@ -0,0 +1,18 @@
+import { mockFavorites } from "@/lib/mock"
+
+export function listFavorites() {
+  return mockFavorites
+}
+
+export function listFavoritesByUser(userId: string) {
+  return mockFavorites.filter((favorite) => favorite.userId === userId)
+}
+
+export function isFavorited(userId: string, targetType: "player" | "shop", targetId: string) {
+  return mockFavorites.some(
+    (favorite) =>
+      favorite.userId === userId &&
+      favorite.targetType === targetType &&
+      favorite.targetId === targetId,
+  )
+}