Default to using system clock to infer user timezone on js clients

Using system clock to infer user timezone on clients makes Khoj
more robust to provide location aware responses.

Previously only ip based location was used to infer timezone via API.
This didn't provide any decent fallback when calls to ipapi failed or
Khoj was being run in offline mode

src/interface/web/app/chat/page.tsx

@@ -136,7 +136,9 @@ export default function Chat() {
     const [uploadedFiles, setUploadedFiles] = useState<string[]>([]);
     const [image64, setImage64] = useState<string>("");
 
-    const locationData = useIPLocationData();
+    const locationData = useIPLocationData() || {
+        timezone: Intl.DateTimeFormat().resolvedOptions().timeZone,
+    };
     const authenticatedData = useAuthenticatedData();
     const isMobileWidth = useIsMobileWidth();