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

apps/docs/content/(01-linear-structures)/two-pointers/344-reverse-string.mdx

@@ -2,13 +2,15 @@
 title: '344. Reverse String'
 description: Write a function that reverses a string. The input string is given as an array of characters s
 icon: dot
+topics:
+  - { name: "Two Pointers", slug: "two-pointers" }
+  - { name: "String", slug: "string" }
+video: "_d0T_2Lk2qA"
 sidebar:
   label: 'Reverse String'
   badge: 'Easy'
 ---
 
-<Badge variant="accent">Two Pointers</Badge>
-
 :::warning
 You must do this by modifying the input array in-place with O(1) extra memory.
 :::
@@ -56,7 +58,3 @@ var reverseString = function(s) {
     }   
 };
 ```
-
-## Explanation
-
-<YouTube id="_d0T_2Lk2qA" title="Reverse String - 3 Ways - Leetcode 344 - Python" />