refactor(docker): use environment variables instead of hardcoded CMD args

Replace hardcoded CMD arguments with ENV directives:
- AETHERA_LISTEN=0.0.0.0
- AETHERA_PORT=8080
- AETHERA_DATA_DIR=/app/data

This allows runtime configuration via docker run -e or compose files.

Dockerfile

@@ -61,8 +61,10 @@ RUN mkdir -p /app/data
 # Expose the default port
 EXPOSE 8080
 
+# Set environment variable defaults
+ENV AETHERA_LISTEN=0.0.0.0
+ENV AETHERA_PORT=8080
+ENV AETHERA_DATA_DIR=/app/data
+
 # Set the entrypoint
 ENTRYPOINT ["./aethera"]
-
-# Default command with recommended production settings
-CMD ["--listen", "0.0.0.0", "--port", "8080", "--data-dir", "/app/data"]