fix failing build

[heinrich10]

What?

Fixes TypeScript compilation errors that caused npm run build to fail.

Why?

The project build was broken after stricter TypeScript/ESLint type checking was introduced. Three files no longer compiled:

• scripts/migrate.ts — Kysely's Migrator returns error as unknown, but the local variable was typed Error | undefined.
• test/api_tests/helper.ts — The mocked response body was typed as Record<string, unknown>, which prevented downstream casts to PaginatedResponse<T>.
• test/api_tests/person.test.ts — body.errors is optional (unknown[] | undefined), so accessing .length directly violated strict null checks.

How?

• Updated error type to unknown in scripts/migrate.ts.
• Changed the response body type to unknown in test/api_tests/helper.ts.
• Replaced body.errors.length with body.errors?.length in test/api_tests/person.test.ts.

Testing?

• npm run build ✅
• npm run lint ✅
• npm test ✅ (32/32 tests passing)

Screenshots (optional)

N/A

Anything Else?

N/A

AI Summary (optional)

Fixed TypeScript build errors by aligning variable types with Kysely's API and applying optional chaining for nullable error arrays.