fix: normalize YouTube proxy URL and support dashboard fields

Rewrite https proxy URLs to http, allow HOST/PORT/USER/PASSWORD env vars,
and surface clearer errors when proxies fail on the wrong port.

Co-authored-by: Cursor <cursoragent@cursor.com>

compose.yml

@@ -9,6 +9,10 @@ services:
       - OPENROUTER_API_KEY=${OPENROUTER_API_KEY}
       - OPENROUTER_MODEL=${OPENROUTER_MODEL:-google/gemini-2.5-flash}
       - YOUTUBE_PROXY=${YOUTUBE_PROXY:-}
+      - YOUTUBE_PROXY_HOST=${YOUTUBE_PROXY_HOST:-}
+      - YOUTUBE_PROXY_PORT=${YOUTUBE_PROXY_PORT:-0}
+      - YOUTUBE_PROXY_USER=${YOUTUBE_PROXY_USER:-}
+      - YOUTUBE_PROXY_PASSWORD=${YOUTUBE_PROXY_PASSWORD:-}
       - WEBSHARE_PROXY_USERNAME=${WEBSHARE_PROXY_USERNAME:-}
       - WEBSHARE_PROXY_PASSWORD=${WEBSHARE_PROXY_PASSWORD:-}
       - WEBSHARE_PROXY_LOCATIONS=${WEBSHARE_PROXY_LOCATIONS:-}