docker instructions cleanup

Dockerfile

@@ -1,13 +1,33 @@
-FROM python:3.11-slim
+FROM python:3.12-slim
 
-RUN apt-get update && apt-get install -y \
+# Set environment variables
+ENV PYTHONUNBUFFERED=1 \
+    PYTHONDONTWRITEBYTECODE=1 \
+    PIP_NO_CACHE_DIR=1
+
+# Create non-root user
+RUN useradd -m -s /bin/bash user
+
+# Install system dependencies
+RUN apt-get update && apt-get install -y --no-install-recommends \
     tree \
     && rm -rf /var/lib/apt/lists/*
 
-RUN useradd -m -s /bin/bash user
-
 WORKDIR /app
+
+# Copy all necessary files for package installation
+COPY pyproject.toml README.md ./
+
+# Copy the package source
+COPY repo_to_text ./repo_to_text
+
+# Install the package
+RUN pip install --no-cache-dir -e .
+
+# Copy remaining files
 COPY . .
-RUN pip install -e . && pip install pyperclip
+
+# Set default user
+USER user
 
 ENTRYPOINT ["repo-to-text"]