feat(auth): unify mobile-first authentication flow

src/api/users.ts

@@ -7,6 +7,18 @@ const normalizeDigits = (value: string) =>
 
 // --- Auth Endpoints ---
 
+export type ResolveAuthMobileStatus = "existing_user" | "new_user"
+
+export const resolveAuthMobile = async (mobile: string): Promise<{ status: ResolveAuthMobileStatus }> => {
+  const normalizedMobile = normalizeDigits(mobile)
+  const response = await authFetch("/api/users/auth/resolve-mobile/", {
+    method: "POST",
+    body: JSON.stringify({ mobile: normalizedMobile }),
+  })
+  if (!response.ok) throw await buildApiError(response)
+  return response.json()
+}
+
 export const loginWithPassword = async (mobile: string, password: string) => {
   const normalizedMobile = normalizeDigits(mobile)
   const response = await authFetch('/api/users/login/', {