feat(02-01): create internal/auth package skeleton, test DB harness, env docs
- auth/doc.go: package comment explaining consolidated layout (Open Question 3 resolved)
- auth/types.go: User + Session structs, SessionCookieName (D-12), SessionTTL (D-09),
SessionExtendThreshold (D-09), ErrSessionNotFound, ErrInvalidHash, ErrIncompatibleVersion
- auth/testdb_test.go: setupTestDB creates isolated per-test schema (test_<uuid>),
runs goose Up with unique version table, drops schema on cleanup (D-26)
TestSetupTestDB_Roundtrip smoke test verifies users table visible
- go.mod: added github.com/pressly/goose/v3 v3.27.1 as direct dependency
- .env.example: added TEST_DATABASE_URL and SESSION_SECRET with comments (D-14, D-26)
2c84f4275b