CRAFT-2074-eslint-v9-migration

[valoriecarli]

experimental branch under test to be linked in with commercetools/merchant-center-application-kit#3931

---

Background
The appkit eslint9 PR introduces:

• New package- @commercetools-frontend/eslint-config-mc-app-flat for ESLint 9 + flat config support
• ESLint 9 compatibility- Upgraded to TypeScript ESLint v8, eslint-plugin-jest v28, and other ESLint 9-compatible
  plugins
• Flat config format - Modern array-based configuration replacing legacy .eslintrc format
• Deprecation of @commercetools-frontend/eslint-config-mc-app (ESLint 8 only)

---

This PR consumes the ESLint 9 migration changes from ☝🏻 and makes the following changes to accommodate it:

1. Migrated to ESLint 9 Flat Config

• Removed legacy .eslintrc.js and .eslintignore files
• Added eslint.config.js (flat config format)
• Extends @commercetools-frontend/eslint-config-mc-app-flat
• Custom rules for ui-kit specific needs (testing-library overrides)

2. Dependency updates:

• @commercetools-frontend/eslint-config-mc-app-flat - currently linked to file:./vendor/...-hash.tgz--> NEEDS TO BE DELETED AND ADDED TO GITIGNORE. linked to test CI runs.
• @typescript-eslint/eslint-plugin
• @typescript-eslint/parser
• eslint
• eslint-formatter-pretty

3. Misc

• Fixed linting issues caught by stricter rules
• Updated imports in generators

Once complete, we can close out:

• chore(deps): update dependency eslint-formatter-pretty to v6 - abandoned #3024
• chore(deps): update dependency eslint to v9 #3023

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Project	Deployment	Actions	Updated (UTC)
ui-kit	Ready	Preview, Comment	Feb 4, 2026 8:45pm

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