feat(extract): GISCO extractor + wire all unscheduled extractors

- New gisco.py: proper extractor module replacing scripts/download_gisco_nuts.py.
  Writes uncompressed .geojson (ST_Read can't handle .gz). Fixed partition path
  gisco/2024/01/nuts2_boundaries.geojson; cursor tracking skips re-download monthly.
- all.py: import + register gisco in EXTRACTORS (9 independent, 1 dep)
- pyproject.toml: add extract-gisco entry point
- workflows.toml: add census_usa, census_usa_income, eurostat_city_labels,
  ons_uk, gisco — all monthly, no dependencies
- Delete scripts/download_gisco_nuts.py (superseded)

Unblocks: stg_nuts2_boundaries, stg_regional_income, stg_income_usa,
and 4 downstream models (dim_locations, pseo_city_costs_de,
location_opportunity_profile, pseo_country_overview).

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

extract/padelnomics_extract/pyproject.toml

@@ -21,6 +21,7 @@ extract-census-usa = "padelnomics_extract.census_usa:main"
 extract-census-usa-income = "padelnomics_extract.census_usa_income:main"
 extract-ons-uk = "padelnomics_extract.ons_uk:main"
 extract-geonames = "padelnomics_extract.geonames:main"
+extract-gisco = "padelnomics_extract.gisco:main"
 
 [build-system]
 requires = ["hatchling"]