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/stack/0155-min-stack.org

@@ -1,18 +1,118 @@
 #+PROPERTY: STUDY_DECK_02
 * TODO 0155. Min Stack :medium:
 :PROPERTIES:
-:NEETCODE: [[file:../../roadmap.org::*0155. Min Stack][Roadmap]]
+:NEETCODE: [[file:../../roadmap.org::*0155. Min Stack][0155. Min Stack]]
 :END:
 
+Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.
+
+Implement the ~MinStack~ class:
+
+ - ~MinStack()~ initializes the stack object.
+
+ - ~void push(int val)~ pushes the element ~val~ onto the stack.
+
+ - ~void pop()~ removes the element on the top of the stack.
+
+ - ~int top()~ gets the top element of the stack.
+
+ - ~int getMin()~ retrieves the minimum element in the stack.
+
+You must implement a solution with ~O(1)~ time complexity for each function.
+
+*Example 1:*
+
+
+#+begin_src
+Input
+["MinStack","push","push","push","getMin","pop","top","getMin"]
+[[],[-2],[0],[-3],[],[],[],[]]
+
+Output
+[null,null,null,null,-3,null,0,-2]
+
+Explanation
+MinStack minStack = new MinStack();
+minStack.push(-2);
+minStack.push(0);
+minStack.push(-3);
+minStack.getMin(); // return -3
+minStack.pop();
+minStack.top();    // return 0
+minStack.getMin(); // return -2
+#+end_src
+
+
+*Constraints:*
+
+ - ~-2^{31} <= val <= 2^{31} - 1~
+
+ - Methods ~pop~, ~top~ and ~getMin~ operations will always be called on *non-empty* stacks.
+
+ - At most ~3 * 10^{4}~ calls will be made to ~push~, ~pop~, ~top~, and ~getMin~.
+
 ** TODO Approach
 Write your approach here.
 
 ** TODO Python
 #+begin_src python
+class MinStack:
 
+    def __init__(self):
+        
+
+    def push(self, val: int) -> None:
+        
+
+    def pop(self) -> None:
+        
+
+    def top(self) -> int:
+        
+
+    def getMin(self) -> int:
+        
+
+
+# Your MinStack object will be instantiated and called as such:
+# obj = MinStack()
+# obj.push(val)
+# obj.pop()
+# param_3 = obj.top()
+# param_4 = obj.getMin()
 #+end_src
 
 ** TODO C++
 #+begin_src cpp
+class MinStack {
+public:
+    MinStack() {
+        
+    }
+    
+    void push(int val) {
+        
+    }
+    
+    void pop() {
+        
+    }
+    
+    int top() {
+        
+    }
+    
+    int getMin() {
+        
+    }
+};
 
+/**
+ * Your MinStack object will be instantiated and called as such:
+ * MinStack* obj = new MinStack();
+ * obj->push(val);
+ * obj->pop();
+ * int param_3 = obj->top();
+ * int param_4 = obj->getMin();
+ */
 #+end_src