Keycloak 26.x exposes dedicated health endpoints on the management
port (9000) via /health/live and /health/ready. The previous probes
used GET / on port 8080 which redirects to the configured KC_HOSTNAME
(HTTPS), causing kubelet to fail the probe with "Probe terminated
redirects" and eventually kill the pod in a crashloop.

Changes:
- Add KC_HEALTH_ENABLED=true to activate health endpoints
- Expose management port 9000 in container ports
- Switch liveness probe to /health/live on port 9000
- Switch readiness probe to /health/ready on port 9000
- Increase failure thresholds for more tolerance during startup

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: mattia-eleuteri <mattia@hidora.io>
(cherry picked from commit 0873691)

Use a startupProbe to defer liveness/readiness checks until Keycloak
has fully started, instead of relying on initialDelaySeconds. This is
more robust for applications with variable startup times.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: mattia-eleuteri <mattia@hidora.io>
(cherry picked from commit d18ed79)