Fix emailed invitation expiry handling

[rafiki270]

Summary

• align the durable team invitation and emailed token to one 24-hour validity window
• renew both deadlines on resend or same-address re-invite
• show Invitation expired only for elapsed deadlines and Invitation invalid for every other unusable state
• enforce the same classification on direct and PKCE-bearing email invitation paths
• update invitation email copy, API descriptions, product documentation, and regression coverage

Testing

• pnpm build
• pnpm lint
• pnpm typecheck
• pnpm test (1934 passed, 374 skipped)
• pnpm --filter @uoa/api exec vitest run tests/unit/auth-registration-email-link.service.test.ts tests/unit/team-invite-token.service.test.ts tests/unit/email-registration-link.route.test.ts tests/unit/team-invite-page.service.test.ts (28 passed)
• git diff --check