Support shareable application links for mailing reminders

[danielsjoo]

Summary

• Make application preview/edit URLs shareable by UUID and load their metadata through the ownership-checked backend endpoint.
• Preserve the target through initial session loading, sign-in, refresh, and new tabs; reject invalid or unavailable links without rendering PDF controls.
• Show the application title, wrap the mobile toolbar, allow Director access, and respect staff-only manual mailing controls.

Verification

• npm run build passed (existing large-chunk warning).
• npm run lint:ts passed with 19 existing warnings and zero errors; npm run lint:scss passed.
• npx vitest run src/components/Applications/applicationLinks.test.tsx --environment jsdom: 5 tests passed.
• Playwright against the local backend: logged-out link/sign-in return, new tab, refresh, edit/cancel preserving the UUID, manual-mailed status persistence, and unavailable links at desktop/mobile widths.

Screenshots

Synthetic local demo data only. Desktop and mobile are paired for each state.

Ready to mail:

Marked mailed and reloaded:

Unavailable link:

Notes

• Deploy backend #168 first: UUID links require GET /api/applications/{id}. Existing state-based navigation remains supported. Scheduler rollout is in infra #13.
• No production data changed and no Slack messages sent. Scheduler activation is separate in the infra PR.