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/0022-generate-parentheses.org

@@ -1,18 +1,46 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0022. Generate Parentheses :medium:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0022. Generate Parentheses][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0022. Generate Parentheses][0022. Generate Parentheses]]
 :END:
 
+Given ~n~ pairs of parentheses, write a function to /generate all combinations of well-formed parentheses/.
+
+*Example 1:*
+
+
+#+begin_src
+Input: n = 3
+Output: ["((()))","(()())","(())()","()(())","()()()"]
+#+end_src
+*Example 2:*
+
+
+#+begin_src
+Input: n = 1
+Output: ["()"]
+#+end_src
+
+
+*Constraints:*
+
+ - ~1 <= n <= 8~
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def generateParenthesis(self, n: int) -> List[str]:
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    vector<string> generateParenthesis(int n) {
+        
+    }
+};
 #+end_src