Fix ByondUI small map preview (#90277)

## About The Pull Request
This PR should fix the problem of small previews in TGUI once and for
all (I hope).

What was causing it? Because TGUI takes a long time to open, that's why
previews were generated broken (small).

On Byond 515 this problem was not so noticeable as the interfaces opened
faster, but with the release of 516 it became much worse.
Previews were generated inside a window that was not yet open, so the
scale was broken, sometimes the window would open before the preview was
done and sent, usually with small interfaces, or when reopening.

I'm not very good at working with signals, and to tell the truth this is
my second experience with them, so I hope I did it right.

## Why It's Good For The Game
No more small map previews

<details> <summary> Video </summary>


https://github.com/user-attachments/assets/834f3820-cc6a-4f65-90e5-d6bb2a118bcf

</details>

## Changelog

🆑
fix: Fixed small character preview, color matrix preview, mech preview,
and other previews with uses ByondUI map
/🆑

---------

Co-authored-by: Gaxeer <44334376+Gaxeer@users.noreply.github.com>

code/modules/modular_computers/file_system/programs/secureye.dm

@@ -28,9 +28,7 @@
 	var/turf/last_camera_turf
 
 	// Stuff needed to render the map
-	var/atom/movable/screen/map_view/cam_screen
-	/// All the plane masters that need to be applied.
-	var/atom/movable/screen/background/cam_background
+	var/atom/movable/screen/map_view/camera/cam_screen
 
 	///Internal tracker used to find a specific person and keep them on cameras.
 	var/datum/trackable/internal_tracker
@@ -75,13 +73,9 @@
 	// Initialize map objects
 	cam_screen = new
 	cam_screen.generate_view(map_name)
-	cam_background = new
-	cam_background.assigned_map = map_name
-	cam_background.del_on_map_removal = FALSE
 
 /datum/computer_file/program/secureye/Destroy()
 	QDEL_NULL(cam_screen)
-	QDEL_NULL(cam_background)
 	QDEL_NULL(internal_tracker)
 	last_camera_turf = null
 	return ..()
@@ -102,8 +96,7 @@
 	if(is_living)
 		concurrent_users += user_ref
 	// Register map objects
-	cam_screen.display_to(user)
-	user.client.register_map_obj(cam_background)
+	cam_screen.display_to(user, ui.window)
 
 /datum/computer_file/program/secureye/ui_status(mob/user, datum/ui_state/state)
 	. = ..()
@@ -197,7 +190,7 @@
 	var/obj/machinery/camera/active_camera = camera_ref?.resolve()
 	// Show static if can't use the camera
 	if(!active_camera?.can_use())
-		show_camera_static()
+		cam_screen.show_camera_static()
 		return
 
 	var/list/visible_turfs = list()
@@ -225,13 +218,6 @@
 	var/size_x = bbox[3] - bbox[1] + 1
 	var/size_y = bbox[4] - bbox[2] + 1
 
-	cam_screen.vis_contents = visible_turfs
-	cam_background.icon_state = "clear"
-	cam_background.fill_rect(1, 1, size_x, size_y)
-
-/datum/computer_file/program/secureye/proc/show_camera_static()
-	cam_screen.vis_contents.Cut()
-	cam_background.icon_state = "scanline2"
-	cam_background.fill_rect(1, 1, DEFAULT_MAP_SIZE, DEFAULT_MAP_SIZE)
+	cam_screen.show_camera(visible_turfs, size_x, size_y)
 
 #undef DEFAULT_MAP_SIZE