rename Event to ReflexEvent

[adhami3310]

fixes #5726

[greptile-apps]

Greptile Summary

This PR fixes a critical production bug by renaming the JavaScript Event constructor to ReflexEvent throughout the codebase. The change addresses issue #5726 where rx.call_script with callbacks would fail in production environments due to a naming conflict with the browser's native DOM Event constructor.

The root problem was that Reflex generated JavaScript code calling Event(...) as a function, but the browser's native Event constructor must be called with the new operator. This worked fine in development but caused TypeError: Failed to construct Event: Please use the new operator exceptions in production builds where minification made this conflict more apparent.

The PR systematically updates six files across the codebase:

• Backend changes: Updates reflex/constants/compiler.py to change the TO_EVENT constant from "Event" to "ReflexEvent", modifies reflex/event.py to use ReflexEvent in event creation logic, updates reflex/utils/format.py to generate ReflexEvent() calls instead of Event() calls, and changes reflex/components/component.py to reference "ReflexEvent" in useCallback dependencies
• Frontend changes: Updates reflex/.templates/web/utils/state.js to rename the Event function to ReflexEvent and all its references, and modifies reflex/compiler/templates.py to generate ReflexEvent constructor calls in compiled templates

This change maintains full backward compatibility at the API level while eliminating the JavaScript namespace collision. The fix ensures that event handling works consistently across both development and production environments, particularly for features like rx.call_script with callback functionality.

Confidence score: 5/5

• This PR is extremely safe to merge with minimal risk as it fixes a critical production bug without breaking existing functionality
• Score reflects a thorough, systematic fix across all relevant files with clear understanding of the root cause and comprehensive solution
• No files require special attention as the changes are straightforward variable/function renamings with consistent implementation across the entire codebase

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[codspeed-hq]

CodSpeed Performance Report

Merging #5735 will not alter performance

_{Comparing rename-Event-to-ReflexEvent (22c7e18) with main (fe9551d)}

Summary

✅ 8 untouched benchmarks