refactor(ai): enhance item structure generation with schema validation
feat(ai): add token usage tracking and cost calculation
fix(ui): improve item card number formatting with locale support
docs(items): add documentation for item value separation
test(items): add tests for value field validation
Add login and register dialogs, user dropdown menu with profile link and logout option, and integrate with session management hook. Prevent hydration mismatches by conditionally rendering auth elements after mount. Update package-lock.json with new @esbuild dependencies for build tooling.