Refactor Config_Web to use heap-allocated JSON document and add stack usage check script

scripts/check_config_web_stack_usage.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+cd "$(dirname "$0")/.."
+
+if rg -n '^[[:space:]]+StaticJsonDocument<kConfigJsonCapacity>[[:space:]]+[A-Za-z_][A-Za-z0-9_]*;' src/Config_Web.cpp; then
+	echo "Config_Web.cpp still allocates kConfigJsonCapacity-sized StaticJsonDocument on the stack" >&2
+	exit 1
+fi
+
+echo "Config_Web.cpp avoids stack-local kConfigJsonCapacity StaticJsonDocument allocations"