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/math-geometry/0066-plus-one.org

@@ -1,18 +1,72 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0066. Plus One :easy:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0066. Plus One][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0066. Plus One][0066. Plus One]]
 :END:
 
+You are given a *large integer* represented as an integer array ~digits~, where each ~digits[i]~ is the ~i^{th}~ digit of the integer. The digits are ordered from most significant to least significant in left-to-right order. The large integer does not contain any leading ~0~'s.
+
+Increment the large integer by one and return /the resulting array of digits/.
+
+*Example 1:*
+
+
+#+begin_src
+Input: digits = [1,2,3]
+Output: [1,2,4]
+Explanation: The array represents the integer 123.
+Incrementing by one gives 123 + 1 = 124.
+Thus, the result should be [1,2,4].
+#+end_src
+
+
+*Example 2:*
+
+
+#+begin_src
+Input: digits = [4,3,2,1]
+Output: [4,3,2,2]
+Explanation: The array represents the integer 4321.
+Incrementing by one gives 4321 + 1 = 4322.
+Thus, the result should be [4,3,2,2].
+#+end_src
+
+
+*Example 3:*
+
+
+#+begin_src
+Input: digits = [9]
+Output: [1,0]
+Explanation: The array represents the integer 9.
+Incrementing by one gives 9 + 1 = 10.
+Thus, the result should be [1,0].
+#+end_src
+
+
+*Constraints:*
+
+ - ~1 <= digits.length <= 100~
+
+ - ~0 <= digits[i] <= 9~
+
+ - ~digits~ does not contain any leading ~0~'s.
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def plusOne(self, digits: List[int]) -> List[int]:
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    vector<int> plusOne(vector<int>& digits) {
+        
+    }
+};
 #+end_src