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)/binary-search/704-binary-search.mdx

@@ -2,13 +2,15 @@
 title: '704. Binary Search'
 description: Given an array of integers nums which is sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then return its index. Otherwise, return -1
 icon: dot
+topics:
+  - { name: "Array", slug: "array" }
+  - { name: "Binary Search", slug: "binary-search" }
+video: "s4DPM8ct1pI"
 sidebar:
   label: 'Binary Search'
   badge: 'Easy'
 ---
 
-<Badge variant="accent">Array</Badge>
-
 ::::warning
 You must write an algorithm with O(log n) runtime complexity.
 ::::
@@ -71,7 +73,3 @@ var search = function(nums, target) {
     return -1;
 };
 ```
-
-## Explanation
-
-<YouTube id="s4DPM8ct1pI" title="Binary Search - Leetcode 704 - Python" />