test: add error boundary tests and configure jest-dom

[HimanshuGaur14]

Description

Fixes #391

Changes made

• app/(root)/dashboard/error.test.tsx (new) — 3 test cases verifying the correct emoji renders for each error type:
  - ⏳ for rate-limit errors ("API limit reached")
  - 🕵️‍♂️ for not-found errors ("User not found")
  - ⚠️ for generic errors

• vitest.setup.ts (new) — registers @testing-library/jest-dom matchers with Vitest so toBeInTheDocument() works

• vitest.config.ts (modified) — added setupFiles: ['./vitest.setup.ts'] to load the setup file before tests run

Pillar

• 🎨 Pillar 1 — New Theme Design
• 📐 Pillar 2 — Geometric SVG Improvement
• 🕐 Pillar 3 — Timezone Logic Optimization
• 🛠️ Other (Bug fix, refactoring, docs)

Visual Preview

Checklist before requesting a review:

• I have read the CONTRIBUTING.md file.
• I have tested these changes locally (localhost:3000/api/streak?user=YOUR_USERNAME).
• I have run npm run format and npm run lint locally and resolved all errors (CI will fail otherwise).
• My commits follow the Conventional Commits format (e.g., feat(themes): ..., fix(calculate): ...).
• [] I have updated README.md if I added a new theme or URL parameter.
• I have started the repo.
• I have made sure that i have only one commit to merge in this PR.
• The SVG output matches the CommitPulse "premium quality" aesthetic standard (no raw elements, smooth animations, correct fonts).
• (Recommended) I joined the CommitPulse Discord community for contributor discussions, mentorship, and faster PR support.

[vercel]

@HimanshuGaur14 is attempting to deploy a commit to the jhasourav07's projects Team on Vercel.

A member of the Team first needs to authorize it.

[github-actions]

👋 Hey @HimanshuGaur14, welcome to CommitPulse! 🎉

Thanks for opening your first pull request — this is a big deal and we appreciate the effort!

While you wait for a review, please double-check:

• ✅ You've read the CONTRIBUTING.md checklist
• ✅ npm run lint, npm run format, and npm run test all pass locally
• ✅ Your PR has a visual preview if it touches any SVG output
• 💬 You've joined our Discord for faster PR feedback

A maintainer will review your PR shortly. Hang tight! 🚀

[github-actions]

🚨 Hey @HimanshuGaur14, the CI Pipeline is failing on this PR and it has been marked as status:blocked.

Please fix the issues before this can be reviewed. Here's how:

1. Run checks locally before pushing:

npm run format:check   # Check Prettier formatting
npm run lint           # Run ESLint
npm run typecheck      # TypeScript type check
npm run test           # Run unit tests (Vitest)
npm run build          # Verify production build passes

2. Auto-fix common issues:

npm run format         # Auto-fix formatting with Prettier
npm run lint -- --fix  # Auto-fix lint errors where possible

3. Check the full failure log here:
👉 View CI Run

Once you push a fix and the CI passes, the status:blocked label will be removed automatically. 💪