feat: pull Woodpecker step images through Harbor dockerhub-cache

Only affects .woodpecker.yml (Gitea/local CI). Dockerfiles and
GitHub Actions workflow unchanged — external builds still pull
from Docker Hub directly.

.woodpecker.yml

@@ -4,7 +4,7 @@
 
 steps:
   lint-python:
-    image: python:3.12-slim
+    image: registry.celestium.life/dockerhub-cache/library/python:3.12-slim
     commands:
       - pip install ruff==0.15.10 --quiet
       - ruff --version
@@ -13,7 +13,7 @@ steps:
       event: [push, pull_request]
 
   test-python:
-    image: python:3.12-slim
+    image: registry.celestium.life/dockerhub-cache/library/python:3.12-slim
     commands:
       - pip install -r requirements.txt --quiet
       - pip install hypothesis --quiet
@@ -22,7 +22,7 @@ steps:
       event: [push, pull_request]
 
   test-frontend:
-    image: node:24-slim
+    image: registry.celestium.life/dockerhub-cache/library/node:24-slim
     commands:
       - cd frontend
       - npm ci
@@ -504,7 +504,7 @@ steps:
       - test-frontend
 
   integration-test:
-    image: alpine/k8s:1.30.2
+    image: registry.celestium.life/dockerhub-cache/alpine/k8s:1.30.2
     environment:
       DOCKERHUB_USER:
         from_secret: docker_username
@@ -532,7 +532,7 @@ steps:
       - build-superset
 
   mirror-github:
-    image: alpine/git
+    image: registry.celestium.life/dockerhub-cache/alpine/git
     failure: ignore
     environment:
       GITHUB_SSH_KEY: