FIX guard unsaved configuration changes

[Ching Wei Kang (WilliamK112)]

Description

• warn before discarding unsaved PyRIT Configuration or Environment & Secrets edits
• use React Router navigation blocking for Configuration tab changes, application navigation, and browser Back/Forward
• use a beforeunload guard for refresh, close, and hard navigation
• guard both Configuration and Environment reload actions with the same confirmation dialog
• track dirty content across all loaded environment files, while preserving drafts when switching between files
• reset discarded content before continuing the requested navigation or reload

This builds on the URL-backed Configuration tabs merged in #2606 and is updated onto the current main branch.

Closes #2594.

Tests and Documentation

• npm test -- --runInBand src/components/Configuration/Configuration.test.tsx src/components/Configuration/EnvironmentFiles.test.tsx — 20 passed
• npm run type-check — passed
• npm run lint — passed
• npm run build — passed
• full frontend suite — 1,430 passed; one unrelated LabelsBar click-away test failed both in the full run and in isolation (that component is outside this PR diff)

No documentation changes are needed for this data-loss prevention fix. JupyText was not run because the change is frontend-only.

AI assistance

I used OpenAI Codex to help implement the navigation guards, update tests, merge current main, and run validation. I reviewed the final diff and test results.

[Roman Lutz (romanlutz)]

Re-reviewed a292338 from scratch. Both previous findings are addressed, and I resolved both threads:

• Failed environment-file reloads now preserve unsaved-change protection for retained drafts, including after further editing.
• The router now initializes after authentication restores the requested URL, so the rendered route matches the deep link.

I found no new confirmed production defects.

One caveat remains: some confirmation-dialog tests fail intermittently in JSDOM. In the diagnostic runs, the guard stayed active and the dialog was mounted, but it was marked aria-hidden. I reproduced the same failure with the unchanged shared dialog and tab controls, without this PR's guard or router code. I am therefore not treating it as a new blocking finding against this PR, but the test-reliability issue remains unresolved.