fix: Handle terminate signals in init script

`tini` does not wait for child processes to close, so all processes will be killed immediately. This is why the container stops so fast.

This fix makes the `init` script listen and handle terminate signals. It also ensures that child processes are shut down in reverse order with proper waiting for completion.

docker/init_scripts/init

@@ -115,19 +115,43 @@ watchdog_process_pid() {
 	fi
 }
 
+stop_process_pid() {
+	PROCESS=$1
+	if [[ -f "/tmp/${PROCESS}.pid" ]]; then
+		PID=$(cat "/tmp/${PROCESS}.pid") || true
+		if [[ -d "/proc/${PID}" ]]; then
+			info_log "stopping ${PROCESS}"
+			kill "${PID}" || true
+			# wait for process exit
+			while [ -e "/proc/${PID}" ]; do sleep 0.1; done
+		fi
+	fi
+}
+
+shutdown() {
+	# shutdown in reverse order
+	stop_process_pid scheduler
+	stop_process_pid worker
+	stop_process_pid watcher
+	stop_process_pid nginx
+	stop_process_pid gunicorn
+	stop_process_pid valkey-server
+}
+
 # switch to backend directory
 cd /backend || { error_log "/backend directory doesn't seem to exist"; }
 
 info_log "Starting up, please wait..."
 
+# setup trap handler
+exited=0
+trap 'exited=1 && shutdown' SIGINT SIGTERM EXIT
+
 # clear any leftover PID files
 rm /tmp/*.pid -f
 
 # function definition done, lets start our main loop
-while true; do
-	# check for died processes every 5 seconds
-	sleep 5
-
+while ! ((exited)); do
 	# Start Valkey server if we dont have a corresponding PID file
 	# and REDIS_HOST is not set (which would mean we're using an external Redis/Valkey)
 	if [[ -z ${REDIS_HOST:=""} ]]; then
@@ -138,7 +162,7 @@ while true; do
 	# but only if it was not successful since the last full docker container start
 	if [[ ${ALEMBIC_SUCCESS:="false"} == "false" ]]; then
 		if alembic upgrade head; then
-			debug_log "database schema migrations suceeded"
+			debug_log "database schema migrations succeeded"
 			ALEMBIC_SUCCESS="true"
 		else
 			error_log "Something went horribly wrong with our database"
@@ -165,4 +189,7 @@ while true; do
 	watchdog_process_pid python worker
 	# Start scheduler if we dont have a corresponding PID file
 	watchdog_process_pid python scheduler
+
+	# check for died processes every 5 seconds
+	sleep 5
 done