chore(deps): update golang:1.27.1 docker digest to 45639bc (#197)

## Summary

`k8s/deploy.yaml` takes the image from build-tools: `image: ${IMAGE}` instead of the hard-coded `oci.unbound.se/dancefinder/dancefetcher:${COMMIT}`.

`deploy` substitutes `${IMAGE}` with `<registry>/<owner>/<name>:<tag>`, where the registry comes from the build-tools config and the tag is the value `${COMMIT}` gets today. The rendered reference is unchanged. Moving off `oci.unbound.se` later becomes one change in infra.

Validated on shiny/time-service#864: merged and deployed to AWS staging and Frostmoln staging with the same image. Prerequisites, all merged:
- unboundsoftware/infra#1808: registry in `BUILDTOOLS_FROSTMOLN_STAGING`
- shiny/acctest#952: acctest pins build-tools to the Gitea registry

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: https://gitea.unbound.se/dancefinder/dancefetcher/pulls/196

Dockerfile

@@ -1,4 +1,4 @@
-FROM amd64/golang:1.27.1@sha256:2c9f73fbc9fe381c63ba57bcbab4ea1c9135604011985a0891bc5fe5d1febfca as build
+FROM amd64/golang:1.27.1@sha256:45639bcd15a6137281761fd9451302c5ea6bd591fa493be3da58b1308fa194d5 as build
 WORKDIR /build
 ENV CGO_ENABLED=0
 ADD . /build

k8s/deploy.yaml

@@ -13,7 +13,7 @@ spec:
         spec:
           containers:
             - name: dancefetcher
-              image: oci.unbound.se/dancefinder/dancefetcher:${COMMIT}
+              image: ${IMAGE}
               imagePullPolicy: Always
               resources:
                 limits: