Fix Beds24 token race condition.

Deduplicate in-flight /authentication/token requests per house so
that concurrent page loads do not each trigger a separate token
refresh, which was exhausting the Beds24 rate limit on first load.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

src/lib/beds24.ts

@@ -64,6 +64,7 @@ function getRefreshToken(houseId: string): string | undefined {
 }
 
 const accessTokenCache = new Map<string, { token: string; expiresAt: number }>();
+const pendingTokenRequests = new Map<string, Promise<string>>();
 
 async function getAccessToken(houseId: string): Promise<string> {
   const refreshToken = getRefreshToken(houseId);
@@ -78,6 +79,13 @@ async function getAccessToken(houseId: string): Promise<string> {
     return cached.token;
   }
 
+  const inFlight = pendingTokenRequests.get(houseId);
+  if (inFlight) {
+    return inFlight;
+  }
+
+  const tokenPromise = (async () => {
+    try {
       const response = await fetch(`${BEDS24_API_BASE}/authentication/token`, {
         method: "GET",
         headers: { refreshToken },
@@ -98,6 +106,13 @@ async function getAccessToken(houseId: string): Promise<string> {
       });
 
       return data.token;
+    } finally {
+      pendingTokenRequests.delete(houseId);
+    }
+  })();
+
+  pendingTokenRequests.set(houseId, tokenPromise);
+  return tokenPromise;
 }
 
 async function beds24Get<T>(