Add Circle Opacity controls for cursor rings

[liamcooper]

Summary

• Adds a Circle Opacity slider (0–100%) for the main cursor circle, GCD circle, and cast bar circle on the QoL → Cursor page.
• Applies opacity when rendering each ring; the main cursor circle previously always drew at 100% alpha.
• Moves GCD/Cast opacity out of the custom color picker into the dedicated slider (original defaults: cursor 100%, GCD/Cast 80%).
• Reorganizes option rows so left/right columns stay aligned (opacity paired with Cursor Trail / Attach to Cursor).

Test plan

• Open QoL → Cursor and confirm all three sections show aligned rows (Enable/Color, Texture/Scale, Opacity/Trail or Attach, Instance-only).
• Adjust Circle Opacity for the main cursor ring and confirm the ring fades in-game.
• Enable GCD and Cast circles; adjust opacity and confirm rings respect the slider.
• Reset cursor profile and confirm GCD/Cast default to 80% and main cursor to 100% when unset.
• /reload after changing settings.