fix: include demo data and cache for HF Spaces deployment

feat: add HF Spaces config and API documentation for backend deployment

feat: add Dockerfile for Hugging Face Spaces deployment

fix: pre-submission audit — remove unused files/imports, add .env.example, harden error handling, add project structure and test docs to README

fix: CUSUM test constants, frequency support, code cleanup

feat: add React frontend, rolling forecast, AI chat, CUSUM tuning, CSV download

feat: complete backend - preprocessor, forecaster, calibrator, detector, explainer

chore: initial project structure