Fixed Capacity Stack String - Quant Developer Interview Question

Problem Description

High-frequency trading systems often avoid heap allocations on the critical path to prevent non-deterministic latency spikes caused by memory management. Implementing fixed-capacity containers that reside on the stack ensures predictable performance and trivial destructibility, which is essential for low-latency C++ applications. Task Implement the FixedString<N> class template to store string data in-place using a fixed-size buffer without dynamic memory allocation. The class must be trivially