fix: add automatic subdomain fallback to bypass 403 errors on coomer.su
- Detects HTTP 403 errors during media download.
- Attempts downloading from alternate subdomains (n1 to n10.coomer.su).
- Falls back to original URL if no valid subdomain is found.
- Caches valid subdomains for faster future access.
- Improves reliability of downloads when original subdomain fails.