Update Dockerfile

Dockerfile

@@ -11,12 +11,13 @@ ENV PYTHONUNBUFFERED=1
 RUN apt-get update && apt-get install -y \
     graphviz \
     wkhtmltopdf \
-    && ln -s /usr/bin/dot /usr/local/bin/dot \
-    && ln -s /usr/bin/wkhtmltopdf /usr/local/bin/wkhtmltopdf \
+    && ln -sf /usr/bin/dot /usr/local/bin/dot \
+    && ln -sf /usr/bin/wkhtmltopdf /usr/local/bin/wkhtmltopdf \
     && rm -rf /var/lib/apt/lists/*
 
-# Add /usr/local/bin to PATH so that 'dot' is found
+# Add /usr/local/bin to PATH and set GRAPHVIZ_DOT explicitly
 ENV PATH="/usr/local/bin:${PATH}"
+ENV GRAPHVIZ_DOT="/usr/local/bin/dot"
 
 # Set working directory
 WORKDIR /app