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/localsend.lua

@@ -1,3 +1,5 @@
 -- Float LocalSend and fzf file picker.
-o.window("(Share|localsend)", { float = true, center = true })
-o.window("localsend", { size = { 1100, 700 } })
+local localsend = "(org\\.localsend\\.)?localsend(_app)?"
+o.window("Share", { float = true, center = true })
+o.window(localsend, { float = true, center = true, size = { 1100, 700 } })
+o.transparent_window(localsend)