fix: optimize dockerfile to reduce build space usage

[TimPietrusky]

Motivation

• Implemented multi-stage build to significantly reduce the final image size
• Added aggressive cleanup after each build step to prevent disk space issues
• Used shallow git clones for all repository dependencies
• Split model downloads with cleanup between each to manage disk space
• Optimized runtime image by only including necessary components
• Updated documentation to reflect the changes and improvements

Technical Changes

1. Dockerfile improvements:

   • Split build into builder and runtime stages
   • Consolidated RUN commands to reduce layers
   • Added cleanup after each major step
   • Used --no-install-recommends for apt-get
   • Implemented shallow git clones
   • Added staged model downloads with cleanup

2. Documentation updates:

   • Added CHANGES.md to track optimizations
   • Updated README.md with current information

These changes should resolve the "no space left on device" error during builds while also producing a more optimized final image.