test: add unit and component tests for formular and tables

[biancode]

Context

We want to ship test coverage improvements as a dedicated pull request.

Goal

Add and maintain a separate PR for unit and component tests with a clear issue reference.

Scope

• add unit tests for src/formular/formular.js
• add component tests for src/tables/tables.js
• provide test runner/config support (Vitest + jsdom)
• document runnable npm test scripts

Acceptance Criteria

• tests are grouped into unit and component scope
• npm test runs successfully
• at least core BMI logic, validation, table rendering/filter/sort/delete are covered
• PR references and closes this issue

PR Reference

Use in PR description:

• Closes #