Make application transparency opt-in (#14253)

* Make application transparency opt-in

* Use the transparency helper for Kanagawa

* Address transparency review findings

* Toggle transparency for opaque windows too

default/hypr/apps/steam.lua

@@ -1,4 +1,3 @@
 o.window("steam", { float = true, idle_inhibit = "fullscreen" })
 o.window({ class = "steam", title = "Steam" }, { center = true, size = { 1100, 700 } })
-o.window("steam.*", { tag = "-default-opacity", opacity = "1 1" })
 o.window({ class = "steam", title = "Friends List" }, { size = { 460, 800 } })