Add Bun CI, Dependabot, dependency review, tests, and exports

[tdtgit]

Motivation

• Add automated CI and dependency automation to ensure dependencies and tests run on each PR and push.
• Make utility functions available for testing and reuse by exporting them from the module.
• Add a dependency review workflow to surface dependency changes in PRs.

Description

• Add .github/dependabot.yml to enable weekly Dependabot updates for bun and github-actions with grouped updates and commit-message prefixes.
• Add .github/workflows/ci.yml to run CI on push and pull_request, which checks out code, sets up Bun with oven-sh/setup-bun@v2, installs with bun install --frozen-lockfile, and runs bun test.
• Add .github/workflows/dependency-review.yml to enable the actions/dependency-review-action@v4 on PRs.
• Export normalize and formatTransactionDetails in index.ts so they can be tested and reused, and keep the existing normalization and formatting logic intact.
• Add index.test.ts with unit tests for normalize and formatTransactionDetails and add a test script to package.json mapping to bun test.

Testing

• Ran bun test, which executed the new index.test.ts test suite that covers normalize and formatTransactionDetails, and the tests passed.
• CI workflow will run bun install --frozen-lockfile followed by bun test on push/PR as configured in .github/workflows/ci.yml.
• Dependency review action is configured to run on PRs using actions/dependency-review-action@v4 to fail fast on risky dependency changes.

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Codex Task