v0.6.0

How climate change is felt: heat, rivers and the sea.

• Heat and frost per station (heat_stations.gpkg): hot days ×2, tropical nights ×5,
  frost days halved (1961-1990 → 2016-2025, 10 quality-checked stations).
• Rivers (scripts/09_rivers.py, dist/rivers/): 15 gauges, their DEM-traced catchments
  and flow indicators; summer flow −24% (1991-2020) and −48% (2016-2022/25) at the near-natural
  gauges, much more on the Ebro side.
• Sea (scripts/10_sea.py, dist/sea/): sea temperature +1.0 °C since the 1980s, marine
  heatwave days 18 → 127 a year, sea level +3 mm a year since 1993.
• Website: chapter 06 gains "Beroa egunerokoan", "Ibaiek ur gutxiago" (catchment map) and
  "Itsasoa berotzen" (heatwave days chart); the rain chart moves to the data and the RustGIS
  project.
• RustGIS project: catchments, river gauges, tide gauges and heat stations in the "Klima
  aldaketa" group; sea and water-balance tables.

Assets added: heat_stations.gpkg, river_gauges.gpkg, river_flow_yearly.csv,
sea_annual.csv, marine_heatwaves.csv, tide_gauges.gpkg.

Data: CC BY 4.0 (climate stations: © AEMET, © Météo-France, © Gobierno de Navarra; rivers: Hub’Eau, © MITECO; sea: NOAA, PSMSL), except elevation (Copernicus WorldDEM-30 licence) and peaks (ODbL, © OpenStreetMap contributors); see ATTRIBUTION.md. Code: MIT.