feat: implement billboard monitor support and remove legacy code

manager/state.lua

@@ -55,6 +55,7 @@ S.configDirty = true
 
 function S.bumpStateVersion()
     S.stateVersion = S.stateVersion + 1
+    S.billboardNeedsRedraw = true
 end
 
 -------------------------------------------------
@@ -63,6 +64,7 @@ end
 
 S.needsRedraw = true
 S.smelterNeedsRedraw = true
+S.billboardNeedsRedraw = true
 S.statusMessage = ""
 S.statusColor = colors.white
 S.statusTimer = 0