fix(ci): image pushes read the registry secrets that exist (#1275)

All kaniko image steps (publish.yml build-gateway/build-ci-base/build-*
and ci-image.yml build-ci-base) referenced from_secret: gitea_username /
gitea_password - which do not exist at repo level - while the repo
carries unused REGISTRY_USERNAME/REGISTRY_PASSWORD secrets. Result: every
image push fails at kaniko's push-permission check (measured: 2482 and
2488 build-gateway 'error checking push permissions'; the same auth gap
is documented in ci.yml's step-level pi install comment re ci-base).

Rewire all six references to the REGISTRY_* secrets that exist. If those
credentials are valid, next push pipelines go fully green behind the new
verify gate; if not, the failure moves to an explicit 401 - either way
the ambiguous permission error resolves into a known state.

.woodpecker/ci-image.yml

@@ -22,9 +22,9 @@ steps:
     image: gcr.io/kaniko-project/executor:debug
     environment:
       REGISTRY_USER:
-        from_secret: gitea_username
+        from_secret: REGISTRY_USERNAME
       REGISTRY_PASS:
-        from_secret: gitea_password
+        from_secret: REGISTRY_PASSWORD
       CI_COMMIT_BRANCH: ${CI_COMMIT_BRANCH}
       CI_COMMIT_TAG: ${CI_COMMIT_TAG}
       CI_COMMIT_SHA: ${CI_COMMIT_SHA}

.woodpecker/publish.yml

@@ -270,9 +270,9 @@ steps:
     when: *image_build_when
     environment:
       REGISTRY_USER:
-        from_secret: gitea_username
+        from_secret: REGISTRY_USERNAME
       REGISTRY_PASS:
-        from_secret: gitea_password
+        from_secret: REGISTRY_PASSWORD
       CI_COMMIT_BRANCH: ${CI_COMMIT_BRANCH}
       CI_COMMIT_TAG: ${CI_COMMIT_TAG}
       CI_COMMIT_SHA: ${CI_COMMIT_SHA}
@@ -306,9 +306,9 @@ steps:
     when: *main_image_build_when
     environment:
       REGISTRY_USER:
-        from_secret: gitea_username
+        from_secret: REGISTRY_USERNAME
       REGISTRY_PASS:
-        from_secret: gitea_password
+        from_secret: REGISTRY_PASSWORD
       CI_COMMIT_BRANCH: ${CI_COMMIT_BRANCH}
       CI_COMMIT_TAG: ${CI_COMMIT_TAG}
       CI_COMMIT_SHA: ${CI_COMMIT_SHA}
@@ -333,9 +333,9 @@ steps:
     when: *main_image_build_when
     environment:
       REGISTRY_USER:
-        from_secret: gitea_username
+        from_secret: REGISTRY_USERNAME
       REGISTRY_PASS:
-        from_secret: gitea_password
+        from_secret: REGISTRY_PASSWORD
       CI_COMMIT_BRANCH: ${CI_COMMIT_BRANCH}
       CI_COMMIT_TAG: ${CI_COMMIT_TAG}
       CI_COMMIT_SHA: ${CI_COMMIT_SHA}