Local Postgres: compose, init-dbs.sql, Drizzle config, db scripts

Database infrastructure only - app tables come with Epic 3.

• docker-compose.yml (postgres:16) + override exposing port 5437 with dev creds, healthcheck off
• init-dbs.sql creates portfolio_dev / portfolio_test / portfolio_test_e2e
• Drizzle generate/migrate only (never push); DATABASE_URL vs DATABASE_URL_MIGRATE from day one
• db-wipe / db-seed / db-reset as idempotent tsx scripts (wipe carries the guard); migrations dir in .prettierignore