Fix container startup: plain HTTP behind reverse proxy

- Caddyfile: disable auto_https and admin, listen on :80 only
- docker-compose: bind port only on 127.0.0.1 to avoid public exposure
- bootstrap/app.php: trust all proxies so Laravel generates correct URLs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Caddyfile

@@ -1,18 +1,16 @@
 {
 	frankenphp
-	# E-Mail für Let's Encrypt (TLS-Zertifikate)
-	email {$CADDY_EMAIL}
+	auto_https off
+	admin off
 }
 
-{$SERVER_NAME} {
+:80 {
 	root * /app/public
 
 	encode zstd br gzip
 
-	# PHP-Requests an FrankenPHP übergeben
 	php_server
 
-	# Logs
 	log {
 		output stderr
 		level WARN