db: drizzle schema matching spec 02, initial migrations, settings service

Migration 0000 enables citext; 0001 creates all 39 tables. DB tests use a
throwaway database per file (TEST_DATABASE_URL, derived from .env in dev,
a postgres service in CI). Decision 0002: pg driver and @fastify/cookie.

Task: M1-T1

apps/api/src/db/client.ts

@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+import { fileURLToPath } from 'node:url';
+import { drizzle } from 'drizzle-orm/node-postgres';
+import { migrate } from 'drizzle-orm/node-postgres/migrator';
+import pg from 'pg';
+import * as schema from './schema.ts';
+
+// Next to this file in src/ and in the image (the Dockerfile copies them to dist/db/migrations).
+const MIGRATIONS_DIR = fileURLToPath(new URL('./migrations', import.meta.url));
+
+export function createDb(url: string) {
+  const pool = new pg.Pool({ connectionString: url, max: 10 });
+  const db = drizzle({ client: pool, schema, casing: 'snake_case' });
+  return { db, pool };
+}
+
+export type Db = ReturnType<typeof createDb>['db'];
+
+export async function runMigrations(db: Db): Promise<void> {
+  await migrate(db, { migrationsFolder: MIGRATIONS_DIR });
+}