chore: update Docker configuration and improve health check functionality

- Added Docker health check endpoint to the FastAPI application, returning a 200 status when the app is running.
- Updated Dockerfile to include curl for health checks and modified entrypoint script to exit on errors.
- Enhanced .dockerignore and .gitignore files to exclude coverage and test artifacts.
- Updated docker-compose.prod.yml to specify version.
- Added pytest-cov as a development dependency to improve test coverage reporting.

Dockerfile

@@ -4,16 +4,17 @@
 # --- Stage 1: builder (dependencies only) ---
 FROM python:3.12-slim AS builder
 WORKDIR /app
-COPY requirements.txt .
-RUN pip install --no-cache-dir -r requirements.txt
+COPY pyproject.toml ./
+COPY duty_teller/ ./duty_teller/
+RUN pip install --no-cache-dir .
 
 # --- Stage 2: runtime (minimal final image) ---
 FROM python:3.12-slim
 
 WORKDIR /app
 
-# Install gosu (drop privileges in entrypoint)
-RUN apt-get update && apt-get install -y --no-install-recommends gosu \
+# Install gosu (drop privileges in entrypoint) and curl (for HEALTHCHECK)
+RUN apt-get update && apt-get install -y --no-install-recommends gosu curl \
     && rm -rf /var/lib/apt/lists/*
 
 # Copy installed packages and console scripts from builder (no requirements.txt, no pip layer)
@@ -23,6 +24,7 @@ COPY --from=builder /usr/local/bin /usr/local/bin
 # Application code (duty_teller package + entrypoint, migrations, webapp)
 ENV PYTHONPATH=/app
 COPY main.py pyproject.toml entrypoint.sh ./
+RUN chmod +x entrypoint.sh
 COPY duty_teller/ ./duty_teller/
 COPY alembic/ ./alembic/
 COPY webapp/ ./webapp/
@@ -34,3 +36,6 @@ RUN adduser --disabled-password --gecos "" botuser \
 # Entrypoint runs as root: fix /app/data ownership (for volume mount), run migrations, then exec as botuser
 ENTRYPOINT ["/bin/sh", "./entrypoint.sh"]
 CMD ["python", "main.py"]
+
+HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
+    CMD curl -f http://localhost:8080/health || exit 1