fix(ci): switch back to GitLab's native Container Registry

Confirmed 2026-08-05 the project's Container Registry is now enabled
server-side (visible in the left sidebar under Deploy). That's strictly
better than the GHCR detour: $CI_REGISTRY/$CI_REGISTRY_USER/$CI_REGISTRY_PASSWORD
are predefined GitLab CI variables scoped to this project, so this needs
zero manually-created credentials (no GitHub PAT to hold in CI/CD variables).

.gitlab-ci.yml

@@ -34,15 +34,22 @@
 # known amd64 microk8s clusters, not public multi-arch distribution (that's
 # what the GHCR release workflows are for, untouched by this file).
 #
+# Registry history (so nobody re-litigates this from scratch): GitLab's own
+# Container Registry was the first choice, hit a dead end (registry_external_url
+# alone didn't populate $CI_REGISTRY — see git history of this file around
+# 2026-08-05 for the GHCR detour that followed), then got fixed server-side
+# (gitlab_rails['registry_enabled'] confirmed set — the project's left sidebar
+# now shows "Container Registry" under Deploy). Back on GitLab's native
+# registry since then: it needs zero extra credentials (CI_REGISTRY_* are
+# predefined GitLab CI variables, always present, scoped to this project
+# only), which is strictly better than holding a GitHub PAT in GitLab CI/CD
+# variables just to push images.
+#
 # Prerequisite this file assumes (documented in VNCMAIL-SETUP.md, not
 # something this file can set up itself):
-#   - A GitHub PAT (write:packages) for ghcr.io/brvncde-dotcom as
-#     $GITLAB_CI_GHCR_TOKEN, plus the matching GitHub username as
-#     $GITLAB_CI_GHCR_USER — both masked/protected CI/CD variables.
-#     GitLab's own Container Registry was tried first (registry_external_url
-#     alone isn't enough - gitlab_rails['registry_enabled'] = true is a
-#     separate config key that never got set, so CI_REGISTRY stayed empty);
-#     revisit switching back once that's actually confirmed working.
+#   - GitLab Container Registry enabled for this project (confirmed 2026-08-05
+#     — "Container Registry" appears in the project's left sidebar under
+#     Deploy / Packages and registries).
 #   - A GitLab Runner (any kind — no cluster access needed at all now).
 #   - Either "allow this job token to push to this project" enabled
 #     (Settings → CI/CD → Job token permissions), OR a project access token
@@ -60,17 +67,11 @@ stages:
   - bump-prod
 
 variables:
-  # Reverted to GHCR 2026-08-05: GitLab's own Container Registry never made
-  # it past "the registry service responds" - the Rails app itself never
-  # picked it up (no project-settings toggle appeared, CI_REGISTRY stayed
-  # empty even after the omnibus registry_external_url config), most likely
-  # because gitlab_rails['registry_enabled'] = true was never separately
-  # set. That's a second, distinct config key from registry_external_url -
-  # revisit switching back once/if that's actually confirmed on the server.
-  # Same image name the sandbox already ran before this pipeline existed
-  # (confirmed public - no imagePullSecrets needed, see
-  # base/deployment.yaml's history), so this is a revert, not a new risk.
-  IMAGE: ghcr.io/brvncde-dotcom/vncmail-plus-dev
+  # GitLab's own registry, scoped to this project. $CI_REGISTRY_IMAGE is a
+  # predefined GitLab CI variable (populated automatically once the Container
+  # Registry is enabled for the project) — no manual image name to keep in
+  # sync, no external credential.
+  IMAGE: $CI_REGISTRY_IMAGE
   GIT_STRATEGY: clone
 
 # ---------------------------------------------------------------------------
@@ -102,11 +103,10 @@ build:
   rules:
     - if: '$CI_PIPELINE_SOURCE == "push" && $CI_COMMIT_BRANCH == "dev"'
   before_script:
-    # GHCR needs a real GitHub PAT (write:packages) as GITLAB_CI_GHCR_TOKEN,
-    # plus GITLAB_CI_GHCR_USER (the GitHub username the PAT belongs to) —
-    # both as masked/protected CI/CD variables. Nothing GitLab-native can
-    # substitute here; a GitHub credential has to come from GitHub.
-    - echo "$GITLAB_CI_GHCR_TOKEN" | docker login ghcr.io -u "$GITLAB_CI_GHCR_USER" --password-stdin
+    # $CI_REGISTRY / $CI_REGISTRY_USER / $CI_REGISTRY_PASSWORD are predefined
+    # GitLab CI variables — populated automatically now that this project's
+    # Container Registry is enabled. No CI/CD variable to create by hand.
+    - echo "$CI_REGISTRY_PASSWORD" | docker login "$CI_REGISTRY" -u "$CI_REGISTRY_USER" --password-stdin
   script:
     - docker build --build-arg GIT_COMMIT=$CI_COMMIT_SHA -t "$IMAGE:sha-$CI_COMMIT_SHORT_SHA" -t "$IMAGE:dev-latest" .
     - docker push "$IMAGE:sha-$CI_COMMIT_SHORT_SHA"