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/0338-counting-bits.org

@@ -1,18 +1,65 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0338. Counting Bits :easy:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0338. Counting Bits][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0338. Counting Bits][0338. Counting Bits]]
 :END:
 
+Given an integer ~n~, return /an array /~ans~/ of length /~n + 1~/ such that for each /~i~/ /(~0 <= i <= n~)/, /~ans[i]~/ is the *number of */~1~/*'s* in the binary representation of /~i~.
+
+*Example 1:*
+
+
+#+begin_src
+Input: n = 2
+Output: [0,1,1]
+Explanation:
+0 --> 0
+1 --> 1
+2 --> 10
+#+end_src
+
+
+*Example 2:*
+
+
+#+begin_src
+Input: n = 5
+Output: [0,1,1,2,1,2]
+Explanation:
+0 --> 0
+1 --> 1
+2 --> 10
+3 --> 11
+4 --> 100
+5 --> 101
+#+end_src
+
+
+*Constraints:*
+
+ - ~0 <= n <= 10^{5}~
+
+*Follow up:*
+
+ - It is very easy to come up with a solution with a runtime of ~O(n log n)~. Can you do it in linear time ~O(n)~ and possibly in a single pass?
+
+ - Can you do it without using any built-in function (i.e., like ~__builtin_popcount~ in C++)?
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def countBits(self, n: int) -> List[int]:
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    vector<int> countBits(int n) {
+        
+    }
+};
 #+end_src