Route all nalog.ru API traffic through SOCKS proxy. Uses NALOGO_PROXY_URL
env var (falls back to PROXY_URL if not set). Adds httpx[socks] dependency.
- Thread proxy_url through Client → AuthProviderImpl + AsyncHTTPClient
- Extract mask_proxy_url() and sanitize_proxy_error() utilities
- Add socks5h:// scheme support for remote DNS resolution
- Sanitize proxy credentials in error messages
- Log masked proxy URL at startup and service init
Fringg