feat: Add custom health percentage color system for all units

[adan291]

Pull Request: Modular Custom Health Percentage Color System

Overview

This PR introduces a modular custom health percentage color system for all unit frames (Player, Target, TargetOfTarget, Pet, Focus, FocusTarget), allowing users to customize health bar colors with 5 configurable color points (0%, 25%, 50%, 75%, 100%).

Key Features

• 5 Fixed Color Points: Users can configure colors at 0%, 25%, 50%, 75%, and 100% health
• Toggle-able Points: Intermediate points (25%, 50%, 75%) can be enabled/disabled
• Editable Percentages: Intermediate points can have their percentage values adjusted
• Mandatory Endpoints: 0% and 100% points are always enabled for gradient consistency
• Smooth Gradients: Automatic color interpolation between enabled points using oUF's colorSmooth
• Reset to Defaults: One-click button to restore default color configuration
• Backward Compatible: Automatically migrates old data structure to new format
• Mutual Exclusion: Cannot be active at the same time as "Colour by Class"

Technical Implementation

Modular Design

All custom logic is contained in a single independent module (Core/CustomHealthColors.lua - 300+ lines), making it:

• Easy to maintain and extend
• Never overwritten during base addon updates
• Simple to disable if needed
• Clean separation of concerns

Minimal Impact on Base Code

Only 4 files modified with minimal changes:

1. Core/Init.xml (1 line added)

   • Loads the custom module

2. Core/Config/GUI.lua (~70 lines)

   • Creates GUI for all unit frames (except boss)
   • Delegates widget creation to custom module
   • Implements mutual exclusion with "Colour by Class"
   • Falls back gracefully if module not loaded

3. Elements/HealthBar.lua (~20 lines in 2 locations)

   • Applies color curve using custom module
   • Clears curve when disabled
   • Includes fallback logic

4. Core/Defaults.lua (data structure update)

   • New array-based structure for all units (Player, Target, TargetOfTarget, Pet, Focus, FocusTarget)
   • Consistent structure across all unit frames

Data Structure

New Structure (All Units):

HealthPercentColors = {
    {percent = 0,    color = {1, 0, 0},     enabled = true},   -- Red (0%)
    {percent = 0.25, color = {1, 0.5, 0},   enabled = false},  -- Orange (25%)
    {percent = 0.50, color = {1, 1, 0},     enabled = false},  -- Yellow (50%)
    {percent = 0.75, color = {0.5, 1, 0},   enabled = false},  -- Light Green (75%)
    {percent = 1.0,  color = {0, 1, 0},     enabled = true},   -- Green (100%)
}