chore: enable eslint rules set 1 and resolve test overrides

[aminamos]

Summary:

Resolves #162.
Enables eslint rule set 1 across codebase and configures scoped overrides for test suites.

Expected behavior:

Linter runs cleanly across both application source files and test fixtures.

Testing tips:

1. Checkout feat/162-eslint-set1.
2. Run yarn lint.

Please make sure these boxes are checked before submitting your pull request - thanks!

• Run the unit tests with yarn test to make sure you didn't break anything
• Add or update any needed documentation to the repo
• Format the title like "feat: [new feature short description]". Title must follow the Conventional Commit Specification(https://www.conventionalcommits.org/en/v1.0.0/).
• Linked all relevant issues
• Include screenshot(s) showing how this pull request works and fixes the issue(s)

[vercel]

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