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/0190-reverse-bits.org

@@ -1,18 +1,68 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0190. Reverse Bits :easy:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0190. Reverse Bits][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0190. Reverse Bits][0190. Reverse Bits]]
 :END:
 
+Reverse bits of a given 32 bits signed integer.
+
+*Example 1:*
+
+*Input:* n = 43261596
+
+*Output:* 964176192
+
+*Explanation:*
+
+ Integer
+ Binary
+
+ 43261596
+ 00000010100101000001111010011100
+
+ 964176192
+ 00111001011110000010100101000000
+
+*Example 2:*
+
+*Input:* n = 2147483644
+
+*Output:* 1073741822
+
+*Explanation:*
+
+ Integer
+ Binary
+
+ 2147483644
+ 01111111111111111111111111111100
+
+ 1073741822
+ 00111111111111111111111111111110
+
+*Constraints:*
+
+ - ~0 <= n <= 2^{31} - 2~
+
+ - ~n~ is even.
+
+*Follow up:* If this function is called many times, how would you optimize it?
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def reverseBits(self, n: int) -> int:
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    int reverseBits(int n) {
+        
+    }
+};
 #+end_src