🔧 chore(concepts): replace old concepts index with course overview

- delete outdated concepts index file
- add new course overview file with updated content
- improve structure for better navigation and understanding

Author: vicegd

concepts/00-index.mdx

@@ -0,0 +1,14 @@
+---
+sidebar_position: 1
+title: Course Overview
+---
+
+import ConceptIndex from '@site/src/components/ConceptIndex';
+
+# Concepts
+
+Theoretical foundations and design paradigms behind algorithms and data structures.
+
+## Concept Index
+
+<ConceptIndex />