Fix unit test suite crash (missing jsdom) and resolve failing tests

[ArshVermaGit]

Description

This PR resolves a critical infrastructure issue where the local unit testing suite was failing to start, and patches 4 brittle tests that were failing once the suite booted up.

Resolved Issue

Resolves #1534

Fixes:

• 🐛 Missing Dependency: Installed jsdom as a devDependency to prevent Vitest from throwing a missing environment error on startup.
• 🐛 API Test Assertions: Updated the expected payload in test/user-settings-api.test.ts to include the newly added bio: "" field, properly aligning the mock expectations with the API response.
• 🐛 DOM Selector Ambiguity: Refactored the DOM query in test/components/DashboardHeader.test.tsx from getByText(/Dashboard/i) to getByRole("heading", { name: "Dashboard" }) because the test was accidentally matching the "Dashboard overview" subtitle text.

How to Verify

1. Pull down this branch.
2. Run npm install to grab jsdom.
3. Run npm run test.
4. Verify that all 606 unit tests pass with a 100% success rate.

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[github-actions]

GSSoC Label Checklist 🏷️

@Priyanshu-byte-coder — please apply the appropriate labels before merging:

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[ArshVermaGit]

Hi @Priyanshu-byte-coder ! Issue #1534 has been resolved. Please review the PR and merge it under GSSoC. Thanks!