Debug: Test actual HTTP connectivity to candidate instances in health endpoint

Debug: Add DNS resolution check for Cobalt/Invidious instances to health endpoint

Fix: Force IPv4 in yt-dlp, add YouTube DNS check to health endpoint

Security: Load cookies from YT_COOKIES_B64 secret at startup, remove from repo

Fix: Add curl-cffi and use chrome impersonation in yt-dlp to bypass bot detection without proxies

Fix: Socket monkey-patch for YouTube IP resolution bypass

Fix: Add ca-certificates and DNS health check

Initial ClipForge API deployment