Netguardian darkvision & visual tweaks (#82919)

## About The Pull Request


![image](https://github.com/tgstation/tgstation/assets/7483112/730a8d16-6489-4c7f-8c82-ae0d07598913)

This gives the Netguardian Prime mob a little bit of darkvision.
Reasoning: Some of these netrunning maps (like the alien hive) are very
dark, and this is a robot.

At the same time I added some emissives to its glowing eye and thrusters
to make them appear to emit light, and I removed the bobbing animation
we automate on flying mobs because its icon state has one already.

## Why It's Good For The Game

If we're going to spawn a mob in the dark it should probably be able to
see where it is.

## Changelog

:cl:
balance: Netguardian Prime can see in the dark.
image: You can see Netguardian Prime in the dark.
/:cl:

code/modules/bitrunning/antagonists/netguardian.dm

@@ -45,12 +45,17 @@
 	speech_span = SPAN_ROBOT
 	death_message = "malfunctions!"
 
+	lighting_cutoff_red = 30
+	lighting_cutoff_green = 5
+	lighting_cutoff_blue = 20
+
 	habitable_atmos = null
 	minimum_survivable_temperature = TCMB
 	ai_controller = /datum/ai_controller/basic_controller/netguardian
 
 /mob/living/basic/netguardian/Initialize(mapload)
 	. = ..()
+	ADD_TRAIT(src, TRAIT_NO_FLOATING_ANIM, INNATE_TRAIT)
 	AddComponent(/datum/component/ranged_attacks, \
 		casing_type = /obj/item/ammo_casing/c46x30mm, \
 		projectile_sound = 'sound/weapons/gun/smg/shot.ogg', \
@@ -62,12 +67,19 @@
 	ai_controller.set_blackboard_key(BB_NETGUARDIAN_ROCKET_ABILITY, rockets)
 
 	AddElement(/datum/element/simple_flying)
+	update_appearance(UPDATE_OVERLAYS)
 
 /mob/living/basic/netguardian/death(gibbed)
 	do_sparks(number = 3, cardinal_only = TRUE, source = src)
 	playsound(src, 'sound/mecha/weapdestr.ogg', 100)
 	return ..()
 
+/mob/living/basic/netguardian/update_overlays()
+	. = ..()
+	if (stat == DEAD)
+		return
+	. += emissive_appearance(icon, "netguardian_emissive", src)
+
 /datum/action/cooldown/mob_cooldown/projectile_attack/rapid_fire/netguardian
 	name = "2E Rocket Launcher"
 	button_icon = 'icons/obj/weapons/guns/ammo.dmi'
@@ -82,9 +94,11 @@
 	playsound(player, 'sound/mecha/skyfall_power_up.ogg', 120)
 	player.say("target acquired.", "machine")
 
-	var/mutable_appearance/scan_effect = mutable_appearance('icons/mob/nonhuman-player/netguardian.dmi', "scan")
-	var/mutable_appearance/rocket_effect = mutable_appearance('icons/mob/nonhuman-player/netguardian.dmi', "rockets")
-	var/list/overlays = list(scan_effect, rocket_effect)
+	var/overlay_icon = 'icons/mob/nonhuman-player/netguardian.dmi'
+	var/list/overlays = list()
+	overlays += mutable_appearance(overlay_icon, "scan")
+	overlays += mutable_appearance(overlay_icon, "rockets")
+	overlays += emissive_appearance(overlay_icon, "scan", player)
 	player.add_overlay(overlays)
 
 	StartCooldown()