feat(leaflet): animate overlay using transparent PNG frames for proper alpha; fix(grib): broaden search across cache, include immediate hours, and global recursive scan
fix(export): remove local import causing 'os referenced before assignment'; fix(leaflet): render overlay in iframe srcdoc to ensure JS runs in Gradio; improve GRIB locate/download
feat(ui): add Min dBZ slider; wire to radar rendering; feat(export): add GRIB2 export for radar with values below threshold set to missing using eccodes
fix(radar): remove stray teal dots by suppressing density fallback when raster present; raise radar min threshold to 5 dBZ; set raster opacity to 1.0 for solid look