Previously the session cookie used Secure=NODE_ENV==='production', and the
dev override still runs the standalone build with NODE_ENV=production, so
the cookie was unreachable from phone-on-LAN testing over HTTP. Switching
to CM_DEBUG lets dev (CM_DEBUG=true) drop the Secure flag while keeping
prod (CM_DEBUG=false) safe.
Also wires CM_AGENT_ID/CM_AGENT_PASSWORD/CM_DEBUG into the web-next
service env block so the login Server Action can compare against them.