feat: raid leader UX feedback - clickable rows, bigger icons, sound toggle, spell toggles, translucent bg

[Rubyj]

Changes

1. Sound toggle

• New playSoundOnReady SavedVariable (defaults true)
• Checkbox in Settings under the Columns row: "Play sound when cooldown is ready"
• The alarm sound on cooldown expiry is gated on this setting

2 & 3. Bigger icons + whole-box clickable

• CARD_ICON increased from 26 → 44 px; icon is centered in the card with timer text at the bottom
• Row frames are now Button frames — the entire card/row is the click target
• "Used" / "Reset" button removed; click anywhere on the row to start or reset the timer
• Wide (columns=1) layout also benefits: no button, timer label uses the reclaimed space

4. Per-spell visibility toggles

• New disabledSpells SavedVariable (table of spell id → true)
• Each row in the Settings scroll list now has a "Show" checkbox to the left of the icon
• Unchecking a spell hides it from the tracker immediately via RebuildUI

5. More translucent background

• Main frame backdrop alpha: 0.92 → 0.55
• Title bar alpha: 0.95 → 0.65