ci: switch Go steps to estate gobuilder + S3 build cache

Moves build/test/pre-commit/release Go steps off golang:1.25 and the
old almalinux9-gobuilder onto the verified gobuilder:0.1.2-alma9
image, and wires GOCACHEPROG (go-cache-plugin) at an absolute cache
dir to the shared S3-backed Go cache. Leaves the golangci-lint step
on its dedicated image (gobuilder has no golangci-lint binary) and
leaves the rpm/upload/release steps untouched (no Go toolchain).

.woodpecker/pre-commit.yaml

@@ -3,7 +3,19 @@ when:
 
 steps:
   - name: pre-commit
-    image: git.unkin.net/unkin/almalinux9-gobuilder:20260606
+    image: artifactapi.k8s.syd1.au.unkin.net/docker-internal/gobuilder:0.1.2-alma9
+    environment:
+      GOCACHE_S3_BUCKET: gocache
+      GOCACHE_S3_REGION: us-east-1
+      GOCACHE_S3_ENDPOINT_URL: https://s3.ceph.unkin.net
+      GOCACHE_S3_PATH_STYLE: "true"
+      GOCACHE_KEY_PREFIX: ci-node-lookup
+      GOCACHE_METRICS: "true"
+      GOCACHEPROG: go-cache-plugin --cache-dir=/tmp/gocache
+      AWS_ACCESS_KEY_ID:
+        from_secret: GOCACHE_AWS_ACCESS_KEY_ID
+      AWS_SECRET_ACCESS_KEY:
+        from_secret: GOCACHE_AWS_SECRET_ACCESS_KEY
     commands:
       - uvx pre-commit run --all-files
     backend_options: