fix(pagination): preserve exact totals across page navigation

[HandSonic]

Summary

• Disable next/last navigation once an exact total reaches the current page boundary.
• Preserve a user-requested exact COUNT across matching page responses while invalidating it for refreshes, new queries, and stale count responses.
• Add focused pagination-state coverage.

Verification

• Fork CI: frontend lint/test/build, backend package, Java/JS CodeQL passed.
• npx --yes tsx src/components/Pagination/paginationState.test.ts (10 passing)
• git diff --check
• adversarial review

[openai0229]

The exact-total state logic and stale COUNT protection are reasonable at this head, and the focused tests cover the important page-boundary cases. I did not find a separate logic blocker.

This branch is currently CONFLICTING with substantial newer result-toolbar and pagination changes on main. Please rebase and integrate the state machine into the current toolbar instead of resolving by replacing the current files wholesale, then rerun the frontend suite. The rebased result needs a fresh review because the conflict is in the core implementation files.