I'm getting error 404 while trying to access my spring boot app on Amazon Elastic Bean Stalk

I developed a spring boot application and I've put the following entries in src/main/resources/application.properties:

spring.mvc.view.prefix: /
spring.mvc.view.suffix: .jsp
server.port=5000

Now when I start it (mvn clean spring-boot:run) locally, I'm getting the output Tomcat started on port(s): 5000 (http) and the app is accessible in the browser under http://localhost:5000/welcome .

I created a Java instance in Amazon Elastic Bean Stalk, I've uploaded war, I even opened the port 5000 in the corresponding Security Group on EC2 instance:

but when I now go to http://my-aws-ebs-instance.com/welcome:5000, I'm getting the following message:

Whitelabel Error Page This application has no explicit mapping for /error, so you are seeing this as a fallback.

Thu Dec 20 16:30:33 UTC 2018 There was an unexpected error (type=Not Found, status=404). /welcome.jsp

Why oh why does it happen like this? What did I forget to configure?

----EDIT

as requested, here's the root java class:

package com.hellokoding.auth;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.context.web.SpringBootServletInitializer;

@SpringBootApplication
public class WebApplication extends SpringBootServletInitializer {
    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(WebApplication.class);
    }

    public static void main(String[] args) throws Exception {
        SpringApplication.run(WebApplication.class, args);
    }
}

Here is also the structure of my project with highlighted welcome.jsp page:

When I unzip the generated war file, this is the file structure on my hard drive:

My pom.xml file:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <artifactId>auth</artifactId>
    <name>auth</name>
    <description>my descr</description>
    <packaging>war</packaging>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.3.5.RELEASE</version>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.7</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>

        <dependency>
            <groupId>org.hsqldb</groupId>
            <artifactId>hsqldb</artifactId>
            <scope>runtime</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.apache.tomcat.embed</groupId>
            <artifactId>tomcat-embed-jasper</artifactId>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>8</source>
                    <target>8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

and the UserController class contains:

...

@Controller
@Scope("session")
public class UserController {

@RequestMapping(value = {"/", "/welcome"}, method = RequestMethod.GET)
public String welcome(Model model) {

    return "welcome";
}

...    

I added some logs inside the welcome method and I see it is running correctly. Also, in log files I can see the following entry:

Mapped "{[/ || /welcome],methods=[GET]}" onto public java.lang.String com.hellokoding.auth.web.UserController.welcome(org.springframework.ui.Model)

so I have no idea why this thing does not work. After trying for 11 hours straight to make it work I'm questioning my life choices, and also I'm wondering why anyone would ever use such a stupid framework since it doesn't work ootb.

--- edit:

I've uploaded a simplified code to github https://github.com/nalogowiec/springbootProblem