fix: use ASCII arrow in upload script (Windows cp1252 compatibility)

feat: v3 models - XGBoost R2=0.9866, GradientBoosting R2=0.9860 as default

fix: use as_posix() for HF repo paths (Windows backslash bug in upload)

fix: upload per-subdirectory to avoid commit timeout; fix .hfignore encoding + artifacts/

feat: HF model repo at v1/v2 root; version selector UI with download submenu; artifacts/ out of git

fix: include figures/reports in HF Hub upload; fix unicode print on Windows

feat: full project — ML simulation, dashboard UI, models on HF Hub