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/0062-unique-paths.org

@@ -1,18 +1,56 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0062. Unique Paths :medium:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0062. Unique Paths][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0062. Unique Paths][0062. Unique Paths]]
 :END:
 
+There is a robot on an ~m x n~ grid. The robot is initially located at the *top-left corner* (i.e., ~grid[0][0]~). The robot tries to move to the *bottom-right corner* (i.e., ~grid[m - 1][n - 1]~). The robot can only move either down or right at any point in time.
+
+Given the two integers ~m~ and ~n~, return /the number of possible unique paths that the robot can take to reach the bottom-right corner/.
+
+The test cases are generated so that the answer will be less than or equal to ~2 * 10^{9}~.
+
+*Example 1:*
+
+
+#+begin_src
+Input: m = 3, n = 7
+Output: 28
+#+end_src
+
+
+*Example 2:*
+
+
+#+begin_src
+Input: m = 3, n = 2
+Output: 3
+Explanation: From the top-left corner, there are a total of 3 ways to reach the bottom-right corner:
+1. Right -> Down -> Down
+2. Down -> Down -> Right
+3. Down -> Right -> Down
+#+end_src
+
+
+*Constraints:*
+
+ - ~1 <= m, n <= 100~
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def uniquePaths(self, m: int, n: int) -> int:
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    int uniquePaths(int m, int n) {
+        
+    }
+};
 #+end_src