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/0115-distinct-subsequences.org

@@ -1,18 +1,64 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0115. Distinct Subsequences :hard:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0115. Distinct Subsequences][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0115. Distinct Subsequences][0115. Distinct Subsequences]]
 :END:
 
+Given two strings s and t, return the number of distinct subsequences of s which equals t.
+
+The test cases are generated so that the answer fits on a 32-bit signed integer.
+
+*Example 1:*
+
+
+#+begin_src
+Input: s = "rabbbit", t = "rabbit"
+Output: 3
+Explanation:
+As shown below, there are 3 ways you can generate "rabbit" from s.
+rabbbit
+rabbbit
+rabbbit
+#+end_src
+
+
+*Example 2:*
+
+
+#+begin_src
+Input: s = "babgbag", t = "bag"
+Output: 5
+Explanation:
+As shown below, there are 5 ways you can generate "bag" from s.
+babgbag
+babgbag
+babgbag
+babgbag
+babgbag
+#+end_src
+
+
+*Constraints:*
+
+ - ~1 <= s.length, t.length <= 1000~
+
+ - ~s~ and ~t~ consist of English letters.
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def numDistinct(self, s: str, t: str) -> int:
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    int numDistinct(string s, string t) {
+        
+    }
+};
 #+end_src