climaemet 1.6.0

• Documentation, user-facing messages, and internal code were reviewed and
  refactored with AI assistance to improve consistency, maintainability, wording
  and roxygen2 tag ordering.
• Tests now rely less on live AEMET API calls and cover additional
  forecast-parsing branches using local fixtures.
• Requests now use a configurable timeout via options(climaemet_timeout = 60).
• aemet_api_key() now uses tools::R_user_dir() for persistent API key
  storage. Existing users are migrated automatically to the new location,
  ensuring backward compatibility.
• aemet_forecast_fires() has been updated to support the new API, which now
  returns six risk levels. Risk values are returned as named factors instead of
  numeric level codes.

What's Changed

• Refactor by @dieghernan in #93
• [codex] Refactor tests to reduce online API use by @dieghernan in #94

Full Changelog: v1.5.1...v1.6.0