chore: remove GitLab CI in favor of Forgejo Actions

FluxCD handles deployment automatically via ImagePolicy,
so only build workflow is needed. GitLab CI is redundant.

.gitlab-ci.yml

@@ -1,65 +0,0 @@
-stages:
-  - build
-  - deploy
-
-variables:
-  DOCKER_BUILDKIT: 1
-  CI_BUILDX_ARCHS: "linux/amd64"
-  DOCKER_TLS_CERTDIR: ""
-
-workflow:
-  auto_cancel:
-    on_new_commit: interruptible
-
-build:
-  stage: build
-  interruptible: true
-  tags:
-    - home
-  image: docker:27
-  services:
-    - docker:27-dind
-  before_script:
-    - docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
-  script:
-    # Pull latest image for layer caching (ignore failures if not exists)
-    - docker pull $CI_REGISTRY_IMAGE:latest || true
-    # Build with cache-from for faster builds and inline cache for future builds
-    - docker build
-      --cache-from $CI_REGISTRY_IMAGE:latest
-      --build-arg BUILDKIT_INLINE_CACHE=1
-      -f k8s/Dockerfile
-      -t $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
-      -t $CI_REGISTRY_IMAGE:latest
-      .
-    - docker push $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
-    - docker push $CI_REGISTRY_IMAGE:latest
-  rules:
-    - if: $CI_COMMIT_BRANCH == "main"
-
-deploy:
-  stage: deploy
-  needs:
-    - job: build
-      artifacts: false
-  tags:
-    - home
-  image:
-    name: bitnami/kubectl:latest
-    entrypoint: [""]
-  script:
-    - kubectl config get-contexts
-    - kubectl config use-context towerops/towerops:home-cluster-agent
-    # Set deployment timestamp (ISO 8601 format in UTC)
-    - DEPLOY_TIMESTAMP=$(date -u +"%Y-%m-%dT%H:%M:%SZ")
-    - echo "Deploying at $DEPLOY_TIMESTAMP"
-    # Deploy new version (migrations run on app start)
-    - kubectl set image deployment/towerops towerops=$CI_REGISTRY_IMAGE:$CI_COMMIT_SHA -n towerops
-    - kubectl set env deployment/towerops DEPLOY_TIMESTAMP=$DEPLOY_TIMESTAMP -n towerops
-    # Don't wait for rollout completion - let Kubernetes handle it asynchronously
-  environment:
-    name: production
-    kubernetes:
-      namespace: towerops
-  rules:
-    - if: $CI_COMMIT_BRANCH == "main"