UUF: Background tasks with hosted services: service reg example

### Description

User feedback transferred from UUF system:
"I don't understand how I'm supposed to start doing this with a project targeting the Microsoft.NET.Sdk.Web SDK. It says I can use dependency injection which is great, but there's no documentation on how I should DI the service or build it in Program.cs"

**What the article shows:**

It demonstrates how to implement background services in Worker SDK projects (Microsoft.NET.Sdk.Worker)
It shows the implementation classes and service registration for Worker projects

**What the article is missing:**

It doesn't show how to register these same background services in Web SDK projects (Microsoft.NET.Sdk.Web)
While it mentions that Web SDK projects can use hosted services, it doesn't provide a concrete example of the Program.cs structure for a web application. Consider adding one.

### Page URL

https://learn.microsoft.com/en-us/aspnet/core/fundamentals/host/hosted-services?view=aspnetcore-9.0&tabs=visual-studio

### Content source URL

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/fundamentals/host/hosted-services.md

### Document ID

b2dece1f-15b8-03af-6d52-7cc070432b4b

### Platform Id

397125bc-12c3-8f36-bb0b-efb01a1e9f43

### Article author

@tdykstra

### Metadata

* ID: c3460b0d-9c60-3a06-ac63-18cf990e53c3
* PlatformId: 397125bc-12c3-8f36-bb0b-efb01a1e9f43
* Service: **aspnet-core**
* Sub-service: **fundamentals**

[Related Issues](https://github.com/dotnet/AspNetCore.Docs/issues?q=is%3Aissue+is%3Aopen+b2dece1f-15b8-03af-6d52-7cc070432b4b)