Blackout Glow

[zanthor]

What does this PR do?

Adds a non-transparent glow style for those of us who have trouble seeing the default glows.

How was it tested?

Tested my CDM in multiple keys, raids, etc over the past week - 12.1 client.

Screenshots

In this screenshot you can see the blackout glow (solid red) being applied to several icons when I have a HotJS active.

Checklist

• New settings default OFF (no behavior change without opt-in)
• Zero cost while disabled: no events registered, no polling, no hooks doing work, no frames built
• Cheap while enabled: event-driven (no polling, no timer-based logic, no per-frame allocations)
• No writes onto Blizzard-owned frames (weak-table pattern used); HookScript/hooksecurefunc only, never SetScript on Blizzard frames
• Tested in-game on live; no version gates or pre-Midnight APIs added