refactor: add full documentation and fix theme loading robustness

- Add JSDoc comments across frontend and backend modules
- Improve code readability and maintainability with consistent documentation style
- Document Electron IPC handlers, UI utilities, and theme system
- Add missing function/class documentation in theme loader and app services
- Minor structural improvements and cleanup across Electron main process modules
- Minor fixes on variable names

app/discordRPC.js

@@ -2,12 +2,40 @@ const config = require('../config');
 const RPC = require("discord-rpc");
 const { logger } = require("../server/logger");
 
+/**
+ * Discord Application Client ID used to authenticate the RPC connection.
+ * Comes from the application configuration.
+ */
 const clientId = `${config.DiscordRPCID}`;
+
+/**
+ * Discord RPC client instance using IPC transport.
+ * Maintains a persistent connection with Discord desktop client.
+ */
 const rpc = new RPC.Client({ transport: "ipc" });
 
+/**
+ * Optional interval reference used for future RPC refresh logic.
+ * Currently reserved for potential periodic activity updates.
+ */
 let intervalId;
 
+/**
+ * Initializes Discord Rich Presence (RPC) connection.
+ *
+ * Responsibilities:
+ * - Connect to Discord via IPC transport
+ * - Set application presence (title, state, timestamps, assets)
+ * - Handle connection errors gracefully via logger
+ *
+ * Triggered once during application startup.
+ */
 function startRPC() {
+
+  /**
+   * Rich Presence payload describing current application state
+   * shown in Discord user profile.
+   */
   rpc.on("ready", () => {
     const presence = {
       largeImageKey: "icon",
@@ -27,10 +55,22 @@ function startRPC() {
   });
 }
 
+/**
+ * Gracefully stops Discord Rich Presence connection.
+ *
+ * Responsibilities:
+ * - Clear any running intervals
+ * - Remove current activity from Discord
+ * - Destroy RPC transport connection
+ * - Handle cleanup errors safely
+ */
 async function stopRPC(){
     try {
       if (intervalId) clearInterval(intervalId);
 
+      /**
+       * Ensures RPC connection exists before attempting cleanup.
+       */
       if (rpc && rpc.transport) {
         await rpc.clearActivity()
         await rpc.destroy();