Add a Flask backend + SQLite + HTML/CSS/JS PWA that:
- Polls the CYD /api/latest endpoint
- Stores readings, sessions, and freeform notes in SQLite
- Displays probe cards with target setpoints and preset options
- Renders temperature history with Chart.js
- Serves a PWA manifest and dark-themed dashboard
Also update cyd-bridge/README.md with verified bringup instructions.
