build: optimize Dockerfile for better layer caching and smaller image size

- Combined apt-get commands into a single RUN layer
- Added --no-install-recommends flag to avoid unnecessary packages
- Cleaned up apt cache and removed package lists after installation
- Reordered COPY commands to copy requirements.txt first for better Docker layer caching
- Separated COPY of requirements.txt from the rest of the application code

Dockerfile

@@ -3,13 +3,25 @@ FROM python:3-bookworm
 # Set working directory
 WORKDIR /app
 
-# Install runtime dependencies (minimal)
-RUN apt update && apt install cvs rsh-client cvsps
+# Install runtime dependencies in a single layer and clean up apt cache
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends \
+    cvs \
+    rsh-client \
+    cvsps && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/*
 
-COPY . .
+# Copy requirements first for better layer caching
+COPY requirements.txt .
 
 # Install Python dependencies
 RUN pip install --no-cache-dir -r requirements.txt
+
+# Copy the rest of the application
+COPY . .
+
+# Install the package
 RUN pip install --no-cache-dir -e .
 
 # Set environment variables for configuration (with defaults)
@@ -26,4 +38,4 @@ ENV CVS_URL="" \
 EXPOSE 5000
 
 # Set the entrypoint to run the application with environment variables as command-line arguments
-ENTRYPOINT ["sh", "-c", "python -m cvs_proxy.app --cvs-url \"$CVS_URL\" --repo-checkouts \"$REPO_CHECKOUTS\" ${CVS_MODULE:+--cvs-module \"$CVS_MODULE\"} ${BASEPATH:+--basepath \"$BASEPATH\"} --host \"$FLASK_HOST\" --port \"$FLASK_PORT\" ${FLASK_DEBUG:+--debug}"]
+ENTRYPOINT ["sh", "-c", "python -m cvs_proxy.app --cvs-url \"$CVS_URL\" --repo-checkouts \"$REPO_CHECKOUTS\" ${CVS_MODULE:+--cvs-module \"$CVS_MODULE\"} ${BASEPATH:+--basepath \"$BASEPATH\"} --host \"$FLASK_HOST\" --port \"$FLASK_PORT\" ${FLASK_DEBUG:+--debug}"]