Update Node-RED configuration and documentation for room management

- Added node-red/config_files/flows_cred.json to .gitignore to prevent committing sensitive credentials.
- Updated documentation references to the new location of room-config.js in node-red/config_files/ for clarity.
- Removed the obsolete room-config.js file, centralizing configuration management.

This update enhances security and improves the organization of Node-RED configuration files, ensuring better management of room settings.

node-red/room-config-loader.js

@@ -1,5 +1,5 @@
 // Load room config into global (no require - Function nodes can't use it).
-// 1. Open node-red/room-config.js in the repo.
+// 1. Open node-red/config_files/room-config.js in the repo (mirror of server file).
 // 2. Copy the whole object: from "const ROOM_CONFIG = {" up to "};" (do NOT copy "module.exports").
 // 3. Replace the ROOM_CONFIG below with your paste. Keep the two lines at the end.