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/bit-manipulation/0007-reverse-integer.org

@@ -1,18 +1,59 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0007. Reverse Integer :medium:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0007. Reverse Integer][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0007. Reverse Integer][0007. Reverse Integer]]
 :END:
 
+Given a signed 32-bit integer ~x~, return ~x~/ with its digits reversed/. If reversing ~x~ causes the value to go outside the signed 32-bit integer range ~[-2^{31}, 2^{31} - 1]~, then return ~0~.
+
+*Assume the environment does not allow you to store 64-bit integers (signed or unsigned).*
+
+*Example 1:*
+
+
+#+begin_src
+Input: x = 123
+Output: 321
+#+end_src
+
+
+*Example 2:*
+
+
+#+begin_src
+Input: x = -123
+Output: -321
+#+end_src
+
+
+*Example 3:*
+
+
+#+begin_src
+Input: x = 120
+Output: 21
+#+end_src
+
+
+*Constraints:*
+
+ - ~-2^{31} <= x <= 2^{31} - 1~
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def reverse(self, x: int) -> int:
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    int reverse(int x) {
+        
+    }
+};
 #+end_src