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

.gitea/workflows/ci.yaml

@@ -13,7 +13,7 @@ jobs:
       BUILDTOOLS_CONTENT: ${{ secrets.BUILDTOOLS_CONTENT }}
       GITEA_REPOSITORY: ${{ gitea.repository }}
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
       - uses: buildtool/setup-buildtools-action@v1
       - name: Build and push
         run: unset GITEA_TOKEN && build && push
@@ -27,7 +27,7 @@ jobs:
       GITEA_REPOSITORY: ${{ gitea.repository }}
     environment: prod
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
       - uses: buildtool/setup-buildtools-action@v1
       - name: Deploy
         run: deploy prod

Dockerfile

@@ -1,4 +1,4 @@
-FROM amd64/golang:1.26.0@sha256:9835fb4f8aa06038ca460e300ee3cb8079d0802a1979724cdb455f5784448704 as build
+FROM amd64/golang:1.27.1@sha256:45639bcd15a6137281761fd9451302c5ea6bd591fa493be3da58b1308fa194d5 as build
 WORKDIR /build
 ENV CGO_ENABLED=0
 ADD . /build

go.mod

@@ -2,7 +2,7 @@ module gitlab.com/unboundsoftware/dancefinder/dancefetcher
 
 go 1.24.0
 
-toolchain go1.26.0
+toolchain go1.27.1
 
 require (
 	github.com/alecthomas/kingpin/v2 v2.4.0

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: