Use POST bodies for cross-search filters

[karilint]

Summary

• Add POST body variants for cross-search rows, map localities, and CSV export
• Switch frontend cross-search data requests and CSV export to send filters/sorting/pagination in JSON bodies
• Keep existing GET endpoints working for backwards compatibility
• Store shared TableView filter/sorting/pagination state in sessionStorage and keep browser URLs short with a tableState id across all normal list views
• Prevent refresh/return-to-table from overwriting stored table state with defaults before restoration finishes
• Add API coverage for the new POST body paths and frontend coverage for shortened/restored table-state URLs

Closes #493

Validation

• git diff --check
• npm run lint:backend
• npm run lint:frontend
• npm run tsc:backend
• npm run tsc:frontend
• cd backend && DOTENV_CONFIG_PATH=../.test.env NODE_OPTIONS='-r dotenv/config' npx jest src/api-tests/crossSearch/get.test.ts src/api-tests/crossSearch/export.test.ts --runInBand --config jest-config.js --detectOpenHandles --forceExit
• cd frontend && npx jest src/components/TableView/TableView.test.tsx --runInBand
• npm run lint && npm run tsc via commit hook before the follow-up TableView commits