Update Express to v5.0.0

[mcollina]

Summary

• Update Express dependency from v4.19.2 to v5.0.0
• Fix route parameter compatibility for Express v5 by replacing optional parameter syntax
• Refactor batch endpoint to use separate routes instead of optional parameters
• All tests passing with Express v5

Changes

• package.json: Update Express from ^4.19.2 to ^5.0.0
• examples/express-benchmark-app.js:
  • Replace /batch/:type/:count? route with separate routes for Express v5 compatibility
  • Add handleBatchRequest helper function to handle both /batch/:type/:count and /batch/:type routes
  • Fix linting issues (space before function parentheses)

Test plan

• All existing tests pass
• Benchmark app starts successfully with Express v5
• Both /batch/:type and /batch/:type/:count endpoints work correctly
• No breaking changes to API functionality

This update brings the project up to the latest major version of Express while maintaining backward compatibility for all existing functionality.