Add MAX Mini App frontend flow

app/composables/useMaxMiniApp.ts

@@ -0,0 +1,63 @@
+type MaxMiniAppUser = {
+  id: number | string;
+  first_name?: string;
+  last_name?: string;
+  username?: string;
+  language_code?: string;
+  photo_url?: string;
+};
+
+type MaxWebApp = {
+  initData?: string;
+  initDataUnsafe?: {
+    user?: MaxMiniAppUser;
+    start_param?: string;
+  };
+  ready?: () => void;
+  close?: () => void;
+  openLink?: (url: string) => void;
+  openMaxLink?: (url: string) => void;
+  platform?: string;
+  version?: string;
+};
+
+declare global {
+  interface Window {
+    WebApp?: MaxWebApp;
+  }
+}
+
+function buildDisplayName(user: MaxMiniAppUser | null) {
+  if (!user) {
+    return '';
+  }
+
+  const firstName = String(user.first_name || '').trim();
+  const lastName = String(user.last_name || '').trim();
+  return `${firstName} ${lastName}`.trim() || firstName || String(user.username || '').trim();
+}
+
+export function useMaxMiniApp() {
+  const webApp = computed<MaxWebApp | null>(() => {
+    if (!import.meta.client) {
+      return null;
+    }
+
+    return window.WebApp ?? null;
+  });
+
+  const initData = computed(() => String(webApp.value?.initData || '').trim());
+  const user = computed<MaxMiniAppUser | null>(() => webApp.value?.initDataUnsafe?.user ?? null);
+  const startParam = computed(() => String(webApp.value?.initDataUnsafe?.start_param || '').trim());
+  const isAvailable = computed(() => Boolean(initData.value));
+  const displayName = computed(() => buildDisplayName(user.value));
+
+  return {
+    webApp,
+    initData,
+    user,
+    startParam,
+    isAvailable,
+    displayName,
+  };
+}