Fix: copy README.md to builder stage

Dockerfile

@@ -14,8 +14,8 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     git \
     && rm -rf /var/lib/apt/lists/*
 
-# Copy dependency file
-COPY pyproject.toml .
+# Copy dependency files (README.md required by pyproject.toml)
+COPY pyproject.toml README.md ./
 
 # Install Python dependencies
 RUN pip install --no-cache-dir --upgrade pip && \