Add DEPLOY.md: ports, firewall, RPC credentials, SSL, operation

Also fix the COIN default in docs/environment.rst, and refer to the Palladium
node setup by concept instead of by paths of its repository.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

Dockerfile

@@ -2,7 +2,7 @@
 #
 #   docker compose up -d --build        (see docker-compose.yml and README.md)
 #
-# Runs on the "palladium" network of the node in palladiumcore/docker and reaches it as palladiumd:2332.
+# Runs on the "palladium" network of the Palladium node container and reaches it as palladiumd:2332.
 
 FROM python:3.14-trixie AS builder