Implement Kubernetes Ingress-based API routing for new Angular 17 frontend, replacing Spring Zuul gateway

Replace the legacy Spring Zuul API Gateway with Kubernetes Ingress resources for routing API calls from the new Angular 18 frontend to backend microservices. This migration is part of the overall transition from AngularJS to Angular 18.

Steps: Create dedicated Kubernetes Ingress resources to handle API routing:

• api-backend-ingress.yaml: Handles core API routes (/api/*)
• public-endpoints-ingress.yaml: Manages public endpoints with special authentication handling
• dsce-api-ingress.yaml: Routes Design Studio (DSCE) API calls with proper path preservation
• the new frontend is deployed under https://dev02.ki-lab.nrw/v2
• the legacy (AngularJs) is deployed under https://dev02.ki-lab.nrw/

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