feat: populate note files with problem descriptions and code stubs

Add populate-notes.mjs that fetches problem descriptions and
Python/C++ code stubs from LeetCode's GraphQL API. Populated
all 197 NeetCode 150 note files with:
- Problem description (examples, constraints)
- Python code stub (function signature)
- C++ code stub (function signature + includes)

API responses cached in leetcode/.cache/leetcode/ for instant re-runs.

org/study_deck_02/dsa/sliding-window/0424-longest-repeating-character-replacement.org

@@ -1,18 +1,58 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0424. Longest Repeating Character Replacement :medium:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0424. Longest Repeating Character Replacement][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0424. Longest Repeating Character Replacement][0424. Longest Repeating Character Replacement]]
 :END:
 
+You are given a string ~s~ and an integer ~k~. You can choose any character of the string and change it to any other uppercase English character. You can perform this operation at most ~k~ times.
+
+Return /the length of the longest substring containing the same letter you can get after performing the above operations/.
+
+*Example 1:*
+
+
+#+begin_src
+Input: s = "ABAB", k = 2
+Output: 4
+Explanation: Replace the two 'A's with two 'B's or vice versa.
+#+end_src
+
+
+*Example 2:*
+
+
+#+begin_src
+Input: s = "AABABBA", k = 1
+Output: 4
+Explanation: Replace the one 'A' in the middle with 'B' and form "AABBBBA".
+The substring "BBBB" has the longest repeating letters, which is 4.
+There may exists other ways to achieve this answer too.
+#+end_src
+
+
+*Constraints:*
+
+ - ~1 <= s.length <= 10^{5}~
+
+ - ~s~ consists of only uppercase English letters.
+
+ - ~0 <= k <= s.length~
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def characterReplacement(self, s: str, k: int) -> int:
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    int characterReplacement(string s, int k) {
+        
+    }
+};
 #+end_src