fix(docker): fix keycloak health check and deprecation warnings

Keycloak 26 image does not include curl, so the health check fails.
Switch to bash TCP check against /realms/master. Also replace deprecated
KEYCLOAK_ADMIN env vars with KC_BOOTSTRAP_ADMIN_USERNAME/PASSWORD, remove
obsolete compose version key, and add start_period for slower machines.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -1,13 +1,12 @@
-version: '3.8'
-
 services:
   keycloak:
     image: quay.io/keycloak/keycloak:26.0
     container_name: certifai-keycloak
     environment:
-      KEYCLOAK_ADMIN: admin
-      KEYCLOAK_ADMIN_PASSWORD: admin
+      KC_BOOTSTRAP_ADMIN_USERNAME: admin
+      KC_BOOTSTRAP_ADMIN_PASSWORD: admin
       KC_DB: dev-mem
+      KC_HEALTH_ENABLED: "true"
     ports:
       - "8080:8080"
     command:
@@ -17,10 +16,11 @@ services:
       - ./keycloak/realm-export.json:/opt/keycloak/data/import/realm-export.json:ro
       - ./keycloak/themes/certifai:/opt/keycloak/themes/certifai:ro
     healthcheck:
-      test: ["CMD", "curl", "-f", "http://localhost:8080/health/ready"]
+      test: ["CMD-SHELL", "exec 3<>/dev/tcp/localhost/8080 && echo -e 'GET /realms/master HTTP/1.1\\r\\nHost: localhost\\r\\nConnection: close\\r\\n\\r\\n' >&3 && head -1 <&3 | grep -q '200 OK'"]
       interval: 10s
       timeout: 5s
-      retries: 5
+      retries: 10
+      start_period: 30s
 
   mongo:
     image: mongo:latest