Remove entropy-rng-cam.py and entropy-rng-opencv.py, which were
superseded by entropy.py (args, loop mode, DRBG) and carried the same
unused-entropy bug. Remove the empty 0-byte `file`. Add requirements.txt
with pinned opencv and the FastAPI stack for the upcoming API stage.
Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>
