internal/storage/ provides:
- Open(path) to create or open the SQLite database with WAL journal,
busy timeout, and foreign keys enabled
- Embedded migrations that create the users table on first run
- UserStore with Create, GetByID, GetByEmail, UpdateLastLogin, Delete
- Email normalisation (trim+lowercase) and uniqueness enforcement
with ErrEmailTaken
- ErrNotFound on lookups and deletes
- UUIDv4 IDs auto-generated when caller leaves ID empty
Uses modernc.org/sqlite (pure-Go) so the binary stays CGO-free and
matches Dockerfile.dev's CGO_ENABLED=0.
Tests cover all CRUD operations, email uniqueness (case-insensitive),
WAL mode verification, and ErrNotFound paths.
Closes#8.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
