# SQLite Database Support

## Overview

Add SQLite database support to Sis using the `sqlite-simple` library. On
startup, the server opens a SQLite database (creating the file if it doesn't
exist), enables WAL mode and foreign keys, and makes the connection available.
No tables are created yet — that comes in a later task.

## Architecture

### New dependency

- `sqlite-simple` added to `package.yaml`.

### New module: `Sis.Database`

Exposes one function:

```haskell
openDatabase :: FilePath -> IO Connection
```

Behavior:

- Opens (or creates) the SQLite database file at the given path.
- Enables WAL journal mode (`PRAGMA journal_mode=WAL`).
- Enables foreign keys (`PRAGMA foreign_keys=ON`).
- Returns the `Connection`.

No tables are created in this task. The file will contain only the empty SQLite
schema.

### Server wiring

- New CLI option `--db-path` in `app/Main.hs` with default value `data/sis.db`.
- `main` opens the database connection via `Sis.Database.openDatabase` before
  starting the Warp server.
- The connection is not yet passed into the Orb app — that wiring happens when
  the first table and routes are added in subsequent tasks.

## Data flow

```
startup → parseOptions → openDatabase (creates file, sets pragmas)
                       → start Warp server (connection held, unused for now)
```

## Error handling

- If `openDatabase` fails (e.g., unwritable path, disk full), the exception
  propagates and the server fails to start. This is correct — the server cannot
  function without its database.

## Testing

- The existing `spec` test suite does not require changes since there are no
  new routes or business logic.
- Integration-level tests for database operations will be added when tables
  and queries are introduced in subsequent tasks.