chore: Add Vitest testing infrastructure to web packages

[jade-codes]

Description

Setup Bun's built-in test runner for TDD in all web packages.

Tasks

• Create bunfig.toml with test config in each package
• Add empty test file (src/__tests__/index.test.ts) in each package
• Add test script to each package.json
• Add root bun test command that runs all tests

Acceptance Criteria

• bun test runs from web/ root
• Empty tests pass
• Coverage reporting configured (bun test --coverage)