feat: add Storybook and Chromatic visual regression testing

[mubking]

• Configure Storybook with Next.js adapter
• Add Chromatic CI workflow for visual regression
• Add Button.stories.tsx as first component story
• Keep setup minimal and scoped to visual testing only

Closes #252

Description

Closes #[ISSUE_NUMBER]

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would break existing functionality)
• Refactor (code improvement without functional changes)
• Documentation update

Testing Strategy

• I have run the linter and type checker
• I have added/updated tests
• All existing tests pass

Self-Review Checklist

• My code follows the project's coding style
• I have reviewed my own code for potential issues
• I have added necessary documentation/comments
• I have updated relevant README or docs if needed
• No new warnings or errors are introduced
• Changes are backward-compatible (or documented breaking changes)

[mubking]

@AIAfiz the Chromatic check needs CHROMATIC_PROJECT_TOKEN added to the repo secrets under Settings → Secrets → Actions. Happy to provide the token if you set up the Chromatic project, or I can create one.

[AlAfiz]

@mubking The Chromatic token is added to the repository Action secrets. Go ahead and re-run the checks

[mubking]

@AIAfiz the secret needs to be named exactly CHROMATIC_PROJECT_TOKEN under Settings → Secrets and variables → Actions → Repository secrets. The workflow is still showing "Missing project token" after re-running.

[mubking]

@AIAfiz the current token in the secret is incorrect. Please update CHROMATIC_PROJECT_TOKEN with this value: chpt_9c5eea6394a98ac