feat(api): Drizzle + libsql DB layer with better-auth schema and migrations

apps/api/test/db.test.ts

@@ -0,0 +1,10 @@
+import { describe, it, expect } from 'vitest';
+import { db } from '../src/db/client';
+import { user } from '../src/db/schema';
+
+describe('database', () => {
+  it('can query the migrated user table (empty)', async () => {
+    const rows = await db.select().from(user);
+    expect(rows).toEqual([]);
+  });
+});