feat: add venue schema and Geoapify seed import

[erikbsa]

Summary

• Add PostgreSQL migrations for venues and external source IDs
• Add GraphQL venue types and read queries
• Add a validated, repeatable seed script for normalized Geoapify data
• Document VM development database setup and venue import steps

Notes

• The seed data file is empty and must be populated with verified venue records
• Image, description, price level, rating, and review count are not included in this version
• The migration and seed import must be run against tapfinder_dev

[andss]

Approved as a foundation for the venue database and Geoapify import. The schema and source mapping give us a good starting point, and rerunning the import preserves existing venue IDs.

As agreed, I’ll take over the remaining work in a separate PR:

• Improve validation of coordinates, opening hours and website URLs, with tests.
• Adapt our Geoapify export to the seed format.
• Add the remaining Venue fields (priceLevel, rating, reviewCount, description and imageUrl) and store the original source data.

I’ll complete the validation and format adaptation before the first import into the server database. The additional fields will be introduced through a new migration that preserves existing records and IDs.