Harden web root, secrets and realtime auth

- .htaccess: refuse .git, .env, docker, nodejs, sdlc*, scripts, archives and
  app internals; security headers, HSTS over TLS, optional HTTPS redirect
- uploads served through app/file.php to signed-in users only
- Apache/PHP hardening config for the container (ServerTokens, expose_php)
- least-privilege DB account and APP_SECRET_KEY via docker/php/provision.php;
  SMTP passwords re-encrypted with a random IV (secret_box.php)
- Socket.IO rooms from a PHP-signed token; /emit and cron refuse empty secrets
- escape notification text; CLI guards on build scripts; no fixed demo password

docker/php/config.php.template

@@ -2,14 +2,15 @@
 
 //<><><><><><><><> MAIN CONFIG (docker-generated) <><><><><><><><>//
 if(true){
-	$isTest 		= "master";
 	$base_url		= "/wms-app/";
 	$server_url 	= $base_url."app/";
 	$include_url	= $_SERVER['DOCUMENT_ROOT'].$server_url;
 
 	$db_server		= "db";
-	$db_user 		= "root";
-	$db_pass		= "${DB_ROOT_PASSWORD}";
+	// Least-privilege account created by the entrypoint (docker/php/entrypoint.sh);
+	// root is only used there and by setup.php.
+	$db_user 		= "${DB_APP_USER}";
+	$db_pass		= "${DB_APP_PASSWORD}";
 	$db_type		= "mysql";
 	$db_database 	= "wms";
 	$db_database2 	= "wms2";
@@ -58,7 +59,12 @@ $packages = [
 	],
 ];
 
-// unique key — used for SMTP password encryption, keep consistent across deploys
+// Key for stored SMTP passwords (assets/utils/secret_box.php). Keep it stable
+// across deploys: changing it makes saved SMTP passwords unreadable.
+if (!defined('APP_SECRET_KEY')) {
+	define('APP_SECRET_KEY', '${APP_SECRET_KEY}');
+}
+// Legacy fixed key: only used to read SMTP passwords saved before APP_SECRET_KEY.
 $pinkey = "wms";
 
 $SMTP = [];