feat: add settings menu for UI dimensions

[TheMapperJS]

Added a settings menu to configure the height and width of action bar buttons and unit frames.

Changes:

• Initialized WoWUI_DB.settings for persistent dimension configurations.
• Added /wowui settings slash command to open the configuration interface.
• Created settings.lua with a slider-based GUI for adjusting widths and heights.
• Updated actionbars.lua to dynamically track action bars and provide UpdateActionBarSizes().
• Updated unitframes.lua to track frames and dynamically resize using UpdateUnitFrameSizes().
• Modified initialization logic to correctly load settings when the ADDON_LOADED event fires.

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PR created automatically by Jules for task 14815671052821292713 started by @TheMapperJS

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