When --stealth is enabled, StealthHttpClient was created without
the proxy URL from --proxy, causing all stealth-mode requests to
bypass the proxy.
Also convert SOCKS5 proxy URL to HTTP when passing to wreq-based
StealthHttpClient, because wreq does not support SOCKS5 protocol
(Clash mixed port supports both protocols on the same port).
Fixes proxy connectivity for 'obscura serve --stealth --proxy socks5://...'
Co-authored-by: handsome.cheng <handsome.cheng@temu.com>
