fix(test): fix test case for table deletion and optimize code

ts/smartclickhouse.classes.timedatatable.ts

@@ -270,6 +270,7 @@ export class TimeDataTable {
     return new plugins.smartrx.rxjs.Observable((observer) => {
       const pollInterval = 1000; // Poll every 1 second
       let lastTimestamp: number;
+      let intervalId: NodeJS.Timeout;
 
       const fetchLastEntryTimestamp = async () => {
         const lastEntry = await this.smartClickHouseDbRef.clickhouseHttpClient.queryPromise(`
@@ -292,13 +293,13 @@ export class TimeDataTable {
 
       const startPolling = async () => {
         await fetchLastEntryTimestamp();
-        const intervalId = setInterval(fetchNewEntries, pollInterval);
-
-        // Cleanup on unsubscribe
-        return () => clearInterval(intervalId);
+        intervalId = setInterval(fetchNewEntries, pollInterval);
       };
 
       startPolling().catch((err) => observer.error(err));
+
+      // Cleanup on unsubscribe
+      return () => clearInterval(intervalId);
     });
   }
 }