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/backtracking/1079-letter-tile-possibilities.org

@@ -1,18 +1,62 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 1079. Letter Tile Possibilities :medium:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*1079. Letter Tile Possibilities][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*1079. Letter Tile Possibilities][1079. Letter Tile Possibilities]]
 :END:
 
+You have ~n~ ~tiles~, where each tile has one letter ~tiles[i]~ printed on it.
+
+Return /the number of possible non-empty sequences of letters/ you can make using the letters printed on those ~tiles~.
+
+*Example 1:*
+
+
+#+begin_src
+Input: tiles = "AAB"
+Output: 8
+Explanation: The possible sequences are "A", "B", "AA", "AB", "BA", "AAB", "ABA", "BAA".
+#+end_src
+
+
+*Example 2:*
+
+
+#+begin_src
+Input: tiles = "AAABBC"
+Output: 188
+#+end_src
+
+
+*Example 3:*
+
+
+#+begin_src
+Input: tiles = "V"
+Output: 1
+#+end_src
+
+
+*Constraints:*
+
+ - ~1 <= tiles.length <= 7~
+
+ - ~tiles~ consists of uppercase English letters.
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
-
+class Solution:
+    def numTilePossibilities(self, tiles: str) -> int:
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
-
+class Solution {
+public:
+    int numTilePossibilities(string tiles) {
+        
+    }
+};
 #+end_src