Add /rest/coreDump endpoint

[stamp]

Added a new endpoint, /rest/coreDump, which enables downloading the latest core dump from the CPU. Also introduced a script, save_elf.py, that stores a copy of the ELF file using the SHA-256 hash of the build as the filename.

The core dump includes the same SHA-256 hash from the original build, which makes it easy to match the core dump to the correct ELF file. This allows decoding and analysis of the dump.