v1.1.0: session guard on all game routes + register + sign-in screen (ISS-107)

lib/authClient.ts

@@ -0,0 +1,34 @@
+'use client';
+
+// v1.1.0 (ISS-107) — client-side session handling shared by every authenticated fetcher, the
+// sign-in screen and the admin panel. The server mints sessions at /api/login + /api/register;
+// we only store the id in localStorage and echo it back as X-Flight-Session.
+
+export const SESSION_STORAGE_KEY = 'flight.session';
+
+export function storedSession(): string | null {
+  if (typeof window === 'undefined') return null;
+  try {
+    return window.localStorage.getItem(SESSION_STORAGE_KEY);
+  } catch {
+    return null; // storage blocked (private mode) — treat as signed out
+  }
+}
+
+// Headers for an authenticated fetch. Empty object when no session is stored, so callers can
+// spread it into their existing header objects without branching.
+export function sessionHeaders(session: string | null = storedSession()): Record<string, string> {
+  return session ? { 'X-Flight-Session': session } : {};
+}
+
+export function storeSession(sessionId: string): void {
+  window.localStorage.setItem(SESSION_STORAGE_KEY, sessionId);
+}
+
+export function clearStoredSession(): void {
+  try {
+    window.localStorage.removeItem(SESSION_STORAGE_KEY);
+  } catch {
+    // storage blocked — nothing to clear
+  }
+}