Update webapp-template versions

[milanRasche]

Updated Java 21 LTS to Java 25 LTS

Updated Spring Boot 3.5.5 to Spring Boot 4.0.3
-Used maven OpenRewrite to assist migration

Updated Angular v20 to Angular v21
-Used ng update command

I checked that the app will build and start.
One one cypress test runs as expected.

Closes #13

[stijnpotters1]

Perhaps bump:

  "@angular-eslint/builder": "20.2.0",
  "@angular-eslint/eslint-plugin": "20.2.0",
  "@angular-eslint/eslint-plugin-template": "20.2.0",
  "@angular-eslint/template-parser": "20.2.0",

and

 "angular-eslint": "20.2.0",

to angular 21.2.0 as well?

[milanRasche]

Perhaps bump:

  "@angular-eslint/builder": "20.2.0",
  "@angular-eslint/eslint-plugin": "20.2.0",
  "@angular-eslint/eslint-plugin-template": "20.2.0",
  "@angular-eslint/template-parser": "20.2.0",

and

 "angular-eslint": "20.2.0",

to angular 21.2.0 as well?

Perhaps bump:

  "@angular-eslint/builder": "20.2.0",
  "@angular-eslint/eslint-plugin": "20.2.0",
  "@angular-eslint/eslint-plugin-template": "20.2.0",
  "@angular-eslint/template-parser": "20.2.0",

and

 "angular-eslint": "20.2.0",

to angular 21.2.0 as well?

Yup! Bumped it to 21.2.0.