Fix login hang after PIN + enrich Banquet mode

- Auth: introduce a shared AuthProvider/useAuth so entering the PIN updates
  reactive state and the layout's gate navigates immediately (previously it
  cached the token check at startup, so login appeared to hang until a manual
  refresh). login/scanner now use signIn/signOut.
- Banquet: donor lookup now returns lifetime giving, last-12-months giving
  (computed from dated transactions), member/donor status, bear name, and tags.
  The banquet result screen shows status badge + lifetime and last-year figures.
  Tickets are irrelevant in banquet mode.
- Admin: fix "‹ Scanner" back link wrapping (remove fixed width).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/lib/api.ts

@@ -59,9 +59,17 @@ export async function login(pin: string): Promise<void> {
   await saveToken(token);
 }
 
+// Lets the auth provider react when the token is cleared (e.g. on a 401), so
+// UI state stays in sync with storage.
+let onCleared: (() => void) | null = null;
+export function onAuthCleared(cb: (() => void) | null): void {
+  onCleared = cb;
+}
+
 export async function logout(): Promise<void> {
   cachedToken = null;
   await clearToken();
+  onCleared?.();
 }
 
 async function authed<T>(path: string, init: RequestInit = {}): Promise<T> {
@@ -128,9 +136,14 @@ export interface DonorLookup {
   found: boolean;
   email: string;
   name: string;
+  bearName: string;
+  lifetime: number;
+  lastYear: number;
   online: number;
   offline: number;
-  total: number;
+  isMember: boolean;
+  tags: string[];
+  status: string;
   source: "master" | "transactions" | "none";
 }