Add volcanic-agents token user

Second entry in authorization.users with token auth, no permissions
block (so full admin). Token is supplied via NATS_VOLCANIC_AGENTS_TOKEN
Coolify env var and substituted into the inline config at compose parse
time. Local credentials.local.json (gitignored) holds the connection
details for both users.

.gitignore

@@ -1,4 +1,5 @@
 deploy.json
+credentials.local.json
 
 # .NET build output (for examples/csharp)
 bin/

docker-compose.yml

@@ -39,7 +39,8 @@ configs:
 
       authorization {
         users = [
-          { user: "${NATS_USER}", password: "${NATS_PASSWORD}" }
+          { user: "${NATS_USER}", password: "${NATS_PASSWORD}" },
+          { user: "volcanic-agents", token: "${NATS_VOLCANIC_AGENTS_TOKEN}" }
         ]
       }