feat: Integrate Keycloak as central Identity Provider

Keycloak IDP Integration — Linked Issues

PRD

#540

Epic 1: Keycloak Foundation & User Authentication

#541 (closed)

Stories: #535 (closed) #545 (closed) #555 (closed) #556 (closed) #557 (closed) #558 (closed) #559 (closed) #560 (closed) #561 (closed) #562 (closed) #563 (closed)

QA: #537 (closed) #551 (closed)

Retrospective: #539 (closed)

Epic 2: Secure API Access & Resilient Authentication

#542 (closed)

Stories: #564 (closed) #565 (closed) #566 #567 (closed) #568 (closed) #569 (closed) #570 (closed) #571 (closed)

Retrospective: #552 (closed)

Epic 3: Session Management, User Lifecycle & GDPR

#543 (closed)

Stories: #572 (closed) #573 (closed) #574 (closed) #575 (closed) #576 (closed) #577 (closed) #578 (closed) #548 (closed)

Retrospective: #553 (closed)

Epic 4: Audit Logging & Compliance Reporting

#544 (closed)

Stories: #549 (closed) #550 (closed)

Retrospective: #554 (closed)