fix: properly detect offline mode when using cached data

src/services/dataService.js

@@ -179,7 +179,7 @@ export async function fetchData() {
     const cached = loadFromCache();
     if (cached) {
       console.warn('NocoDB not configured, using cached data');
-      return cached.data;
+      return { data: cached.data, fromCache: true, cacheTimestamp: cached.timestamp };
     }
     throw new Error('NocoDB not configured and no cached data available. Set REACT_APP_NOCODB_URL and REACT_APP_NOCODB_TOKEN in .env.local');
   }
@@ -191,7 +191,7 @@ export async function fetchData() {
     // Save to cache on success
     saveToCache(data);
     
-    return data;
+    return { data, fromCache: false };
   } catch (err) {
     console.error('NocoDB fetch failed:', err.message);
     
@@ -199,7 +199,7 @@ export async function fetchData() {
     const cached = loadFromCache();
     if (cached) {
       console.warn(`Using cached data from ${new Date(cached.timestamp).toLocaleString()} (offline mode)`);
-      return cached.data;
+      return { data: cached.data, fromCache: true, cacheTimestamp: cached.timestamp };
     }
     
     throw new Error(`Database unavailable and no cached data: ${err.message}`);
@@ -214,7 +214,7 @@ export async function refreshData() {
   
   const data = await fetchFromNocoDB();
   saveToCache(data);
-  return data;
+  return { data, fromCache: false };
 }
 
 // ============================================