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

server/helpers/parseInfo.helpers.js

@@ -1,27 +1,38 @@
+/**
+ * Normalizes a video payload by attaching the resource type.
+ *
+ * @param {Object} data - Raw video metadata.
+ * @returns {Object} Normalized video object.
+ */
 function parseVideo(data) {
-
-    return {
-        type: "video",
-        ...data
-    };
+  return {
+    type: "video",
+    ...data
+  };
 }
 
+/**
+ * Transforms a raw playlist payload into a normalized structure
+ * containing playlist metadata and a simplified list of videos.
+ *
+ * @param {Object} data - Raw playlist metadata.
+ * @returns {Object} Normalized playlist object.
+ */
 function parsePlaylist(data) {
-    
-    return {
-        type: "playlist",
-        title: data.title || data.id,
-        channel: data.uploader,
-        count: data.entries.length,
-        videos: (data.entries || []).map(v => ({
-            id: v.id,
-            title: v.title,
-            url: v.webpage_url,
-            duration: v.duration,
-            thumbnail: v.thumbnail,
-            uploader: v.uploader
-        }))
-    };
+  return {
+    type: "playlist",
+    title: data.title || data.id,
+    channel: data.uploader,
+    count: data.entries.length,
+    videos: (data.entries || []).map(v => ({
+      id: v.id,
+      title: v.title,
+      url: v.webpage_url,
+      duration: v.duration,
+      thumbnail: v.thumbnail,
+      uploader: v.uploader
+    }))
+  };
 }
 
-module.exports = { parseVideo, parsePlaylist };
+module.exports = { parseVideo, parsePlaylist };