build(deps): Bump dotnet/aspnet from 8.0 to 9.0 in /EssentialCSharp.Web

Bumps dotnet/aspnet from 8.0 to 9.0.

---
updated-dependencies:
- dependency-name: dotnet/aspnet
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

EssentialCSharp.Web/Dockerfile

@@ -1,6 +1,6 @@
 #syntax=docker/dockerfile:1.2
 
-FROM mcr.microsoft.com/dotnet/aspnet:8.0 AS base
+FROM mcr.microsoft.com/dotnet/aspnet:9.0 AS base
 WORKDIR /app
 EXPOSE 8080
 EXPOSE 8081