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/greedy/0053-maximum-subarray.org

@@ -1,18 +1,64 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0053. Maximum Subarray :medium:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0053. Maximum Subarray][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0053. Maximum Subarray][0053. Maximum Subarray]]
 :END:
 
+Given an integer array ~nums~, find the subarray with the largest sum, and return /its sum/.
+
+*Example 1:*
+
+
+#+begin_src
+Input: nums = [-2,1,-3,4,-1,2,1,-5,4]
+Output: 6
+Explanation: The subarray [4,-1,2,1] has the largest sum 6.
+#+end_src
+
+
+*Example 2:*
+
+
+#+begin_src
+Input: nums = [1]
+Output: 1
+Explanation: The subarray [1] has the largest sum 1.
+#+end_src
+
+
+*Example 3:*
+
+
+#+begin_src
+Input: nums = [5,4,-1,7,8]
+Output: 23
+Explanation: The subarray [5,4,-1,7,8] has the largest sum 23.
+#+end_src
+
+
+*Constraints:*
+
+ - ~1 <= nums.length <= 10^{5}~
+
+ - ~-10^{4} <= nums[i] <= 10^{4}~
+
+*Follow up:* If you have figured out the ~O(n)~ solution, try coding another solution using the *divide and conquer* approach, which is more subtle.
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def maxSubArray(self, nums: List[int]) -> int:
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    int maxSubArray(vector<int>& nums) {
+        
+    }
+};
 #+end_src