Potential fix for code scanning alert no. 7: Inefficient regular expression

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

src/services/social/fetchers/UnifiedFetcher.ts

···
   isValidAccount(account: string): boolean {
     if (!account) return false;
     const handle = this.normalizeHandle(account);
-    return /^[a-zA-Z0-9.-]+(\.[a-zA-Z0-9.-]+)*$/.test(handle);
+    return /^[a-zA-Z0-9-]+(\.[a-zA-Z0-9-]+)*$/.test(handle);
   }
 
   private normalizeHandle(handle: string): string {