Emergency shuttle is aware of security level (#78271)

## About The Pull Request

The emergency shuttle maintains its security level coefficient and does
the calculation instead of outside procs that aren't aware of what alert
it was when the shuttle was first called.

If the shuttle auto-call timer should be capped at the current security
level timer, that can be done in a different PR.

## Why It's Good For The Game

Fixes https://github.com/tgstation/tgstation/issues/78159

## Changelog

🆑 LT3
fix: Emergency shuttle should correctly scale timer up/down when
changing security levels
/🆑

code/modules/shuttle/emergency.dm

@@ -339,15 +339,9 @@
 
 /obj/docking_port/mobile/emergency/request(obj/docking_port/stationary/S, area/signal_origin, reason, red_alert, set_coefficient=null)
 	if(!isnum(set_coefficient))
-		var/security_num = SSsecurity_level.get_current_level_as_number()
-		switch(security_num)
-			if(SEC_LEVEL_GREEN)
-				set_coefficient = 2
-			if(SEC_LEVEL_BLUE)
-				set_coefficient = 1
-			else
-				set_coefficient = 0.5
-	var/call_time = SSshuttle.emergency_call_time * set_coefficient * engine_coeff
+		set_coefficient = SSsecurity_level.current_security_level.shuttle_call_time_mod
+	alert_coeff = set_coefficient
+	var/call_time = SSshuttle.emergency_call_time * alert_coeff * engine_coeff
 	switch(mode)
 		// The shuttle can not normally be called while "recalling", so
 		// if this proc is called, it's via admin fiat

code/modules/shuttle/shuttle.dm

@@ -439,7 +439,8 @@
 	var/current_engine_power = 0
 	///How much engine power (thrust) the shuttle starts with at mapload.
 	var/initial_engine_power = 0
-
+	///Speed multiplier based on station alert level
+	var/alert_coeff = ALERT_COEFF_BLUE
 	///used as a timer (if you want time left to complete move, use timeLeft proc)
 	var/timer
 	var/last_timer_length
@@ -927,6 +928,20 @@
 	last_timer_length *= multiple
 	setTimer(time_remaining)
 
+/obj/docking_port/mobile/proc/alert_coeff_change(new_coeff)
+	if(isnull(new_coeff))
+		return
+
+	var/time_multiplier = new_coeff / alert_coeff
+	var/time_remaining = timer - world.time
+	if(time_remaining < 0 || !last_timer_length)
+		return
+
+	time_remaining *= time_multiplier
+	last_timer_length *= time_multiplier
+	alert_coeff = new_coeff
+	setTimer(time_remaining)
+
 /obj/docking_port/mobile/proc/invertTimer()
 	if(!last_timer_length)
 		return