Add ready check / summon icon position & size customization to raid frames

[nulltyto]

Summary

The ready check and incoming-summon icons on raid/party frames shared a single texture hardcoded to the health-bar center, with no way to move or resize them. They show in the Indicators preview but had no control. This adds one.

What's new

A Ready Check control in the raid/party frame Indicators section, matching the existing Raid Marker control:

• Position dropdown — 9 anchors (Top Left … Center … Bottom Right)
• Icon Size slider — 8–40 (was fixed at 18/20)
• Cog popup — X/Y offset sliders, plus Show Ready Check and Show Incoming Summon toggles (previously always-on with no UI)

The two icons share a texture, so one set of controls drives both (shared position).

Implementation

• Defaults: readyCheckSize (18), readyCheckPosition ("center"), readyCheckOffsetX/Y (0) — renders identically to before by default. New keys added to the indicators party-sync section.
• Real frames: replaced the hardcoded SetPoint with an AnchorReadyCheck() closure (same 9-position pattern as AnchorRaidMarker); UpdateReadyCheck uses the configured size; the three settings-refresh sites re-apply size + anchor live.
• Preview: applies configured size + position so changes update live in the eye preview. Also fixed a pre-existing duplicate local rcStatuses line.
• Options: new dropdown + size slider + cog row after the Raid Marker row.

Notes

• At the default size (18) the summon icon now renders at 18px instead of its old 20px — a 2px change visible only during an actual summon.
• Both files pass luac -p. Verified by inspection/compile; not yet smoke-tested in-client.