Add FastAPI entropy service with simple API-key auth and Dockerfile

api.py runs the camera producer in a background thread and serves the
latest entropy blob over HTTP. Endpoints: GET / (info), GET /healthz
(liveness, unauthenticated), GET /entropy (returns {hex, bits, ts}).
Auth is a single shared secret via X-API-Key header, controlled by the
ENTROPY_API_KEY env var; empty means no auth, so it is easy to start
open and lock down later. All config is via env vars for containers.

Dockerfile uses python:3.12-slim, installs OpenCV runtime libs, pins
deps from requirements.txt, exposes 8000, and has a healthcheck against
/healthz. Run with: docker build -t entropy-rng . && docker run -p 8000:8000 \
-e ENTROPY_CAMERA_URL=http://192.168.0.200/mjpg/video.mjpg entropy-rng

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

Dockerfile

@@ -0,0 +1,26 @@
+FROM python:3.12-slim
+
+# OpenCV runtime libraries
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    libgl1 libglib2.0-0 && \
+    rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY entropy.py health.py api.py ./
+
+ENV ENTROPY_BITS=256 \
+    ENTROPY_INTERVAL=1.0 \
+    ENTROPY_API_KEY="" \
+    UVICORN_HOST=0.0.0.0 \
+    UVICORN_PORT=8000
+
+EXPOSE 8000
+
+HEALTHCHECK --interval=10s --timeout=3s --start-period=15s --retries=3 \
+    CMD python3 -c "import urllib.request,sys; urllib.request.urlopen('http://localhost:8000/healthz').read(); sys.exit(0)" || exit 1
+
+CMD ["sh", "-c", "uvicorn api:app --host ${UVICORN_HOST} --port ${UVICORN_PORT}"]