Standardize deployment env and deployer handling

scripts/deployment/deploy-multisig.sh

@@ -29,13 +29,12 @@ RPC_URL="${RPC_URL:-http://localhost:8545}"
 PRIVATE_KEY="${PRIVATE_KEY:-}"
 OWNERS="${OWNERS:-}"  # Comma-separated list of owner addresses
 
-if [ -z "$PRIVATE_KEY" ]; then
-    echo "Error: PRIVATE_KEY not set"
+if ! require_private_key_env; then
     exit 1
 fi
 
 if [ -z "$OWNERS" ]; then
-    echo "Error: OWNERS not set (comma-separated list)"
+    echo "ERROR: OWNERS not set. Provide a comma-separated owner list." >&2
     exit 1
 fi
 
@@ -59,4 +58,3 @@ echo "Next steps:"
 echo "1. Transfer admin roles to multi-sig address"
 echo "2. Test multi-sig operations"
 echo "3. Document multi-sig procedures"
-