climatekit 0.1.0

• Initial release.
• 10 temperature indices: frost days, ice days, summer days, tropical nights, growing season length, heating/cooling/growing degree days, diurnal temperature range, warm spell duration.
• 8 precipitation indices: consecutive dry/wet days, total precipitation, heavy/very heavy precipitation days, max 1-day and 5-day precipitation, precipitation intensity (SDII).
• 3 drought indices: Standardized Precipitation Index (SPI), Standardized Precipitation-Evapotranspiration Index (SPEI), potential evapotranspiration (Hargreaves method).
• 5 agroclimatic indices: Huglin, Winkler, Branas, first/last frost dates.
• 4 comfort indices: wind chill, heat index, humidex, fire danger index.
• Generic dispatcher ck_compute() for programmatic index selection.
• ck_available() and ck_metadata() for index discovery.
• ck_convert_temp() for temperature unit conversion.