docs(docs): add ProblemBadges component, layout slot, and enrich pages with topics/video frontmatter, plus guide placeholders and topic‑landing map.

apps/docs/content/(02-nodal-grid)/hybrid-structures/146-lru-cache.mdx

@@ -2,13 +2,17 @@
 title: '146. LRU Cache'
 description: Design a data structure that follows the constraints of a Least Recently Used (LRU) cache
 icon: dot
+topics:
+  - { name: "Hash Table", slug: "hash-table" }
+  - { name: "Linked List", slug: "linked-list" }
+  - { name: "Design", slug: "design" }
+  - { name: "Doubly-Linked List", slug: "doubly-linked-list" }
+video: "7ABFKPK2hD4"
 sidebar:
   label: 'LRU Cache'
   badge: 'Medium'
 ---
 
-<Badge variant="accent">Hash Table</Badge>
-
 ### Example 1:
 - Input: ``
 - Output: ``
@@ -110,7 +114,3 @@ class LRUCache:
 # param_1 = obj.get(key)
 # obj.put(key,value)
 ```
-
-## Explanation
-
-<YouTube id="7ABFKPK2hD4" title="LRU Cache - Twitch Interview Question - Leetcode 146" />