Allow larger file uploads

By default, Sirius Web inherits Spring Boot/Tomcat’s upload limit of 1048576 bytes. To support bigger files, raise the multipart limits through configuration properties (environment variables, .properties, or command-line arguments):

spring.servlet.multipart.max-file-size=10MB
spring.servlet.multipart.max-request-size=10MB

Restart the server after changing the values and the application will accept the new size. No change to the Sirius Web JAR is required.