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/1-d-dynamic-programming/0070-climbing-stairs.org

@@ -1,18 +1,57 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0070. Climbing Stairs :easy:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0070. Climbing Stairs][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0070. Climbing Stairs][0070. Climbing Stairs]]
 :END:
 
+You are climbing a staircase. It takes ~n~ steps to reach the top.
+
+Each time you can either climb ~1~ or ~2~ steps. In how many distinct ways can you climb to the top?
+
+*Example 1:*
+
+
+#+begin_src
+Input: n = 2
+Output: 2
+Explanation: There are two ways to climb to the top.
+1. 1 step + 1 step
+2. 2 steps
+#+end_src
+
+
+*Example 2:*
+
+
+#+begin_src
+Input: n = 3
+Output: 3
+Explanation: There are three ways to climb to the top.
+1. 1 step + 1 step + 1 step
+2. 1 step + 2 steps
+3. 2 steps + 1 step
+#+end_src
+
+
+*Constraints:*
+
+ - ~1 <= n <= 45~
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def climbStairs(self, n: int) -> int:
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    int climbStairs(int n) {
+        
+    }
+};
 #+end_src