feat: add modular plugin system and documentation

server/plugins/PLUGINS.md

@@ -0,0 +1,23 @@
+# 🔌 NodeCast TV Plugin System
+
+This directory allows you to extend the functionality of **NodeCast TV** without modifying the core source code. The server automatically detects and loads any `.js` file placed in this folder at startup.
+
+---
+
+## 🛠️ How It Works
+
+The plugin loader in `server/index.js` scans this directory and expects each file to export a **initialization function**. 
+
+When the server starts, it calls this function and passes the internal Express instance and the loaded services.
+
+### Plugin Signature
+Each plugin must follow this structure:
+
+```javascript
+/**
+ * @param {Object} app - The Express application instance
+ * @param {Object} services - Object containing all internal services (db, syncService, etc.)
+ */
+module.exports = function(app, services) {
+    // Your logic here
+};