Allow NUM_WORKERS override (#2776)

Resolves #2610

## Description:

Add NUM_WORKERS env override for server worker count.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:
aotumuri

---------

Co-authored-by: Evan <evanpelle@gmail.com>

startup.sh

@@ -8,6 +8,12 @@ if [ -z "$CF_API_TOKEN" ] || [ -z "$CF_ACCOUNT_ID" ] || [ -z "$SUBDOMAIN" ] || [
     exit 1
 fi
 
+# Require NUM_WORKERS for non-dev environments.
+if [ "${GAME_ENV:-dev}" != "dev" ] && [ -z "$NUM_WORKERS" ]; then
+    echo "Error: NUM_WORKERS must be set for non-dev environments"
+    exit 1
+fi
+
 # Generate a unique tunnel name using timestamp
 TIMESTAMP=$(date +%Y%m%d%H%M%S)
 TUNNEL_NAME="${SUBDOMAIN}-tunnel-${TIMESTAMP}"