Updates seed_amenity_data.py to also seed median_age values in
fact_census where missing, ensuring demographics notebooks work.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Adds script to populate sample amenity data when Toronto Open Data
API doesn't return neighbourhood IDs (requires spatial join).
Run with: make seed-amenities
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>