chore: test infrastructure improvements (#821, #822, #824, #932)

[SharifIbrahimDev]

What does this PR do?
Implements foundational testing infrastructure improvements across the frontend and backend, enabling more robust CI workflows and local development verification.

Why?
Closes #821 — [FE-032] Add API client mocks for lib/api/quests.test.ts to avoid live env dependency
Closes #822 — [FE-033] Split frontend tests into unit and integration scripts
Closes #824 — [FE-035] Add smoke test for root layout hydration with global error boundary
Closes #932 — [BE-021] Add backend .env.test loading strategy for e2e/integration
Type of Change
Infrastructure / Testing
How was it tested?
FE-032/FE-033: MSW lifecycle added (server.listen(), server.close()) to ensure the tests run purely against mocked local state. vitest.config.ts matches script parameters via --exclude and --include to seamlessly split test:unit and test:integration.
FE-035: Basic un-mocked hydration check established via render() guaranteeing global boundaries compile properly.
BE-021: Unified .env.test configuration injected directly into setup-e2e-env.ts matching existing integration strategies.
Checklist
Tests added and passing
Follows project conventions
Risk
None — Purely testing enhancements. Does not impact production artifacts.

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[RUKAYAT-CODER]

Great job so far

There’s just one blocker — the workflow is failing. Could you take a look and fix it so all checks pass?
You could pull from the main to get the changes before pushing.