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/0131-palindrome-partitioning.org

@@ -1,18 +1,48 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0131. Palindrome Partitioning :medium:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0131. Palindrome Partitioning][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0131. Palindrome Partitioning][0131. Palindrome Partitioning]]
 :END:
 
+Given a string ~s~, partition ~s~ such that every substring of the partition is a *palindrome*. Return /all possible palindrome partitioning of /~s~.
+
+*Example 1:*
+
+
+#+begin_src
+Input: s = "aab"
+Output: [["a","a","b"],["aa","b"]]
+#+end_src
+*Example 2:*
+
+
+#+begin_src
+Input: s = "a"
+Output: [["a"]]
+#+end_src
+
+
+*Constraints:*
+
+ - ~1 <= s.length <= 16~
+
+ - ~s~ contains only lowercase English letters.
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def partition(self, s: str) -> List[List[str]]:
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    vector<vector<string>> partition(string s) {
+        
+    }
+};
 #+end_src