extract HTML templates from main.py into ui.py
main.py: 851 → 414 lines. three inline HTML pages (home, status,
memory graph) plus shared CSS/favicon constants moved to ui.py.
main.py now just calls home_page(), status_page(), memory_page().
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>