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/2-d-dynamic-programming/0312-burst-balloons.org

@@ -1,18 +1,59 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0312. Burst Balloons :hard:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0312. Burst Balloons][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0312. Burst Balloons][0312. Burst Balloons]]
 :END:
 
+You are given ~n~ balloons, indexed from ~0~ to ~n - 1~. Each balloon is painted with a number on it represented by an array ~nums~. You are asked to burst all the balloons.
+
+If you burst the ~i^{th}~ balloon, you will get ~nums[i - 1] * nums[i] * nums[i + 1]~ coins. If ~i - 1~ or ~i + 1~ goes out of bounds of the array, then treat it as if there is a balloon with a ~1~ painted on it.
+
+Return /the maximum coins you can collect by bursting the balloons wisely/.
+
+*Example 1:*
+
+
+#+begin_src
+Input: nums = [3,1,5,8]
+Output: 167
+Explanation:
+nums = [3,1,5,8] --> [3,5,8] --> [3,8] --> [8] --> []
+coins =  3*1*5    +   3*5*8   +  1*3*8  + 1*8*1 = 167
+#+end_src
+
+
+*Example 2:*
+
+
+#+begin_src
+Input: nums = [1,5]
+Output: 10
+#+end_src
+
+
+*Constraints:*
+
+ - ~n == nums.length~
+
+ - ~1 <= n <= 300~
+
+ - ~0 <= nums[i] <= 100~
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def maxCoins(self, nums: List[int]) -> int:
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    int maxCoins(vector<int>& nums) {
+        
+    }
+};
 #+end_src