Adds a coordinate-based population lookup as a fallback when string name
matching fails (~29% of cities). Uses bbox pre-filter (0.14° ≈ 15 km) then
ST_Distance_Sphere to find the nearest GeoNames location in the same country.
Fixes localization mismatches: Milano≠Milan, Wien≠Vienna, München≠Munich.
Population cascade: Eurostat EU > US Census > ONS UK > GeoNames string >
GeoNames spatial > 0.
Coverage: 70.5% → 98.5% (5,401 / 5,481 cities with population > 0).
Key cities before/after:
Wien: 0 → 1,691,468
Milano: 0 → 1,371,498
München: already matched by string; verified still correct at 1,488,719
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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