New: Execute Range Indicator

[luispemu]

Summary

This PR adds an Execute Range Indicator for all specializations with execute-style abilities, providing clear visual feedback when a target enters execute range.

Features

Added a real-time Execute Range Indicator.
Supports all execute-style abilities, including Execute, Kill Shot, Shadow Word: Death, and other supported class abilities.
Automatically accounts for specialization- and talent-specific execute thresholds.
Updates dynamically as targets enter or leave execute range.
Designed to be lightweight with minimal runtime overhead.

Benefits

Provides immediate visual feedback when an execute ability becomes available.
Improves combat awareness across all supported specializations.