ci: pull images через repo.nstart.cloud (corp Docker Hub mirror)

Runners в кластере не имеют network access к Docker Hub.
Заменили все base images:
- maven:3.9.9-eclipse-temurin-21 → repo.nstart.cloud/maven:...
- eclipse-temurin:21-jre → repo.nstart.cloud/eclipse-temurin:21-jre
- liquibase/liquibase:4.27.0 → repo.nstart.cloud/liquibase/...
- docker:27 / docker:27-dind → repo.nstart.cloud/docker:...

.gitlab-ci.yml

@@ -23,7 +23,7 @@ cache:
 # ---- TEST stage ----
 maven-test:
   stage: test
-  image: maven:3.9.9-eclipse-temurin-21
+  image: repo.nstart.cloud/maven:3.9.9-eclipse-temurin-21
   script:
     - mvn $MAVEN_CLI_OPTS verify
   artifacts:
@@ -35,7 +35,7 @@ maven-test:
 # ---- BUILD stage (один общий mvn package для всех 4 jar'ов) ----
 maven-package:
   stage: build
-  image: maven:3.9.9-eclipse-temurin-21
+  image: repo.nstart.cloud/maven:3.9.9-eclipse-temurin-21
   script:
     - mvn $MAVEN_CLI_OPTS package -DskipTests
   artifacts:
@@ -50,8 +50,8 @@ maven-package:
 # ---- PUBLISH stage (4 image параллельно) ----
 .docker-image-template: &docker-image
   stage: publish
-  image: docker:27
-  services: [docker:27-dind]
+  image: repo.nstart.cloud/docker:27
+  services: ["repo.nstart.cloud/docker:27-dind"]
   variables:
     DOCKER_TLS_CERTDIR: "/certs"
     # registry.k8s.265.nstart.local — internal insecure HTTP registry, без auth