improve DEMO.md, README.md

fix DEMO.md

improve README.md, DEMO.md

delete unused data from docs/

correct DEMO.md

correct DEMO.md

correct DEMO.md

add DEMO.md

Translate env.example, rewrite README.md

Translate env.example, rewrite README.md

docs: Add comprehensive README.md

fix: Dockerfile - install openai package for AI generation

fix: Dockerfile - copy src/ before pip install -e .

feat: Docker serve/smoke commands with entrypoint.sh

test: Remove test_grouping_by_date.py (edge cases not critical for MVP)