Add deque, list, forward_list, and array containers

[AnshMNSoni]

Problem

The library currently supports vector, stack, and queue, but several foundational C++ sequence containers are missing. These are heavily used in competitive programming and systems design.

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Missing Containers

Container	C++ Equivalent	Description
deque	std::deque<T>	Double-ended queue, O(1) push/pop from both ends
list	std::list<T>	Doubly linked list, O(1) insert/delete anywhere
forward_list	std::forward_list<T>	Singly linked list, memory efficient
array	std::array<T, N>	Fixed-size array with STL-style interface

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Expected API (Example for deque)

from pythonstl import deque

d = deque()
d.push_front(1)
d.push_back(2)
d.pop_front()
d.pop_back()
print(d.front(), d.back(), d.size())

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Checklist

• deque
• list
• forward_list
• array
• Unit tests for each
• Docstrings with time complexity annotations

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Notes

• deque should be the priority as it is used internally by queue and stack in C++ STL.
• All containers should follow the same naming conventions used in existing containers.