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/two-pointers/0344-reverse-string.org

@@ -1,18 +1,53 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0344. Reverse String :easy:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0344. Reverse String][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0344. Reverse String][0344. Reverse String]]
 :END:
 
+Write a function that reverses a string. The input string is given as an array of characters ~s~.
+
+You must do this by modifying the input array in-place with ~O(1)~ extra memory.
+
+*Example 1:*
+
+
+#+begin_src
+Input: s = ["h","e","l","l","o"]
+Output: ["o","l","l","e","h"]
+#+end_src
+*Example 2:*
+
+
+#+begin_src
+Input: s = ["H","a","n","n","a","h"]
+Output: ["h","a","n","n","a","H"]
+#+end_src
+
+
+*Constraints:*
+
+ - ~1 <= s.length <= 10^{5}~
+
+ - ~s[i]~ is a printable ascii character.
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def reverseString(self, s: List[str]) -> None:
+        """
+        Do not return anything, modify s in-place instead.
+        """
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    void reverseString(vector<char>& s) {
+        
+    }
+};
 #+end_src