Align get-started tutorials with Operaton Modeler

[hauptmedia]

Summary

• replace visible Camunda Modeler wording with Operaton Modeler in the DMN decision-table and DRG tutorials
• align archived Java process application and Java EE tutorial steps that instruct users to edit models or forms in the Modeler
• use a local documentation link for the DMN-in-Cockpit reference in the DRG tutorial
• leave install/download wording out of this PR because those pages belong to the existing distribution download update PR (Update Operaton download and modeler links #130)
• leave quick-start deployment/modeling pages out because they are already covered by PR Align quick start deployment with Operaton #126

Verification

• git diff --check
• rg -n "Camunda Modeler" docs/get-started/dmn/model.md docs/get-started/dmn/drg.md docs/get-started/archive/java-process-app/forms.md docs/get-started/archive/java-process-app/service-task.md docs/get-started/archive/javaee7/complete-process.md -S returns no matches
• rg -n "https://docs\.operaton\.org/(docs/)?(documentation|docs/documentation|get-started)" docs/get-started/dmn/model.md docs/get-started/dmn/drg.md docs/get-started/archive/java-process-app/forms.md docs/get-started/archive/java-process-app/service-task.md docs/get-started/archive/javaee7/complete-process.md -S returns no matches
• npm run build succeeds; it still reports known pre-existing broken link/anchor warnings from main