[FEATURE] Decorator / annotation-based rules

[LukasNiessen]

In short

In TS many things use decorators (@Component, @Injectable, @Controller). This lets a rule target decorated things — 'everything with @Controller lives in the web folder', or 'no property may use a field-injection decorator.'

Problem

A large class of architecture rules is naturally expressed against decorators — 'classes decorated with @controller must live in the web layer', 'no property may use field injection (@Inject)', '@entity types belong to the domain'. ArchUnitTS matches on file paths and names but cannot assert on decorators today.

Proposal

Add decorator predicates onto the existing projectFiles(...) chain (class/method/property/parameter, incl. meta-decorators), e.g. projectFiles("src").withDecorator("Controller").should().beInFolder("**/web/**") and projectFiles("src").inFolder("**/domain/**").shouldNot().useDecorator("Inject").

Acceptance criteria

• .withDecorator("Controller") selects classes carrying that decorator, including via a meta-decorator.
• .shouldNot().useDecorator("Inject") fails on a violating element with a clickable location.
• Empty-test protection applies when no decorated elements match.