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/backtracking/0051-n-queens.org

@@ -1,18 +1,53 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0051. N Queens :hard:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0051. N Queens][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0051. N Queens][0051. N Queens]]
 :END:
 
+The *n-queens* puzzle is the problem of placing ~n~ queens on an ~n x n~ chessboard such that no two queens attack each other.
+
+Given an integer ~n~, return /all distinct solutions to the *n-queens puzzle*/. You may return the answer in *any order*.
+
+Each solution contains a distinct board configuration of the n-queens' placement, where ~'Q'~ and ~'.'~ both indicate a queen and an empty space, respectively.
+
+*Example 1:*
+
+
+#+begin_src
+Input: n = 4
+Output: [[".Q..","...Q","Q...","..Q."],["..Q.","Q...","...Q",".Q.."]]
+Explanation: There exist two distinct solutions to the 4-queens puzzle as shown above
+#+end_src
+
+
+*Example 2:*
+
+
+#+begin_src
+Input: n = 1
+Output: [["Q"]]
+#+end_src
+
+
+*Constraints:*
+
+ - ~1 <= n <= 9~
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def solveNQueens(self, n: int) -> List[List[str]]:
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    vector<vector<string>> solveNQueens(int n) {
+        
+    }
+};
 #+end_src