Django cache backend using PostgreSQL UNLOGGED tables

hynek/psycache uses PostgreSQL UNLOGGED tables as a Redis replacement — writes skip the write-ahead log so they're significantly faster, and crash-truncation is acceptable for a cache anyway.

This approach could be ported to Django as a custom BaseCache backend:

• Create an UNLOGGED table instead of DatabaseCache's regular table, via a migration or a custom createcachetable management command
• Reuse Django's existing database connection pool — no extra infrastructure
• Optionally store values as JSONB instead of pickled text, enabling native Postgres querying on cached values
• Postgres-specific, so it would live in a dedicated psycache-django package (~200 lines)

Eliminates Redis as a dependency for teams already on Postgres, with no changes to the rest of the Django cache API.