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);
@@ -78,26 +79,40 @@ async function getAccessToken(houseId: string): Promise<string> {
     return cached.token;
   }
 
-  const response = await fetch(`${BEDS24_API_BASE}/authentication/token`, {
-    method: "GET",
-    headers: { refreshToken },
-  });
-
-  if (!response.ok) {
-    throw new Error(
-      `Beds24 authentication error for house ${houseId}: ${response.status} ${response.statusText}`
-    );
+  const inFlight = pendingTokenRequests.get(houseId);
+  if (inFlight) {
+    return inFlight;
   }
 
-  const data: { token: string; expiresIn: number } = await response.json();
+  const tokenPromise = (async () => {
+    try {
+      const response = await fetch(`${BEDS24_API_BASE}/authentication/token`, {
+        method: "GET",
+        headers: { refreshToken },
+      });
 
-  // Refresh a minute early to avoid using a token that expires mid-request.
-  accessTokenCache.set(houseId, {
-    token: data.token,
-    expiresAt: Date.now() + Math.max(data.expiresIn - 60, 30) * 1000,
-  });
+      if (!response.ok) {
+        throw new Error(
+          `Beds24 authentication error for house ${houseId}: ${response.status} ${response.statusText}`
+        );
+      }
 
-  return data.token;
+      const data: { token: string; expiresIn: number } = await response.json();
+
+      // Refresh a minute early to avoid using a token that expires mid-request.
+      accessTokenCache.set(houseId, {
+        token: data.token,
+        expiresAt: Date.now() + Math.max(data.expiresIn - 60, 30) * 1000,
+      });
+
+      return data.token;
+    } finally {
+      pendingTokenRequests.delete(houseId);
+    }
+  })();
+
+  pendingTokenRequests.set(houseId, tokenPromise);
+  return tokenPromise;
 }
 
 async function beds24Get<T>(