feat(extract): replace OpenWeatherMap with Open-Meteo weather extractor

Replaced the OWM extractor (8 locations, API key required, 14,600-call
backfill over 30+ days) with Open-Meteo (12 locations, no API key,
ERA5 reanalysis, full backfill in 12 API calls ~30 seconds).

- Rename extract/openweathermap → extract/openmeteo (git mv)
- Rewrite api.py: fetch_archive (ERA5, date-range) + fetch_recent (forecast,
  past_days=10 to cover ERA5 lag); 9 daily variables incl. et0 and VPD
- Rewrite execute.py: _split_and_write() unzips parallel arrays into per-day
  flat JSON; no cursor / rate limiting / call cap needed
- Update pipelines.py: --package openmeteo, timeout 120s (was 1200s)
- Update fct_weather_daily.sql: flat Open-Meteo field names (temperature_2m_*
  etc.), remove pressure_afternoon_hpa, add et0_mm + vpd_max_kpa + is_high_vpd
- Remove OPENWEATHERMAP_API_KEY from CLAUDE.md env vars table

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

extract/openmeteo/pyproject.toml

@@ -0,0 +1,20 @@
+[project]
+name = "openmeteo"
+version = "0.1.0"
+description = "Open-Meteo daily weather extractor for coffee-growing regions"
+requires-python = ">=3.13"
+dependencies = [
+    "extract_core",
+    "niquests>=3.14.1",
+]
+
+[project.scripts]
+extract_weather          = "openmeteo.execute:extract_weather"
+extract_weather_backfill = "openmeteo.execute:extract_weather_backfill"
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/openmeteo"]