ci: migrate from GitLab CI to Gitea Actions

- Add Gitea Actions workflow (.gitea/workflows/ci.yaml)
- Update K8s deployment image registry to oci.unbound.se

build-tools-dockerfile

@@ -0,0 +1,10 @@
+FROM amd64/golang:1.25.5@sha256:ad03ba93327b8a6143b49373790b5d92c28067bdb814418509466122ee9c9e63 as builder
+WORKDIR /src
+COPY * ./
+RUN go get
+RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o geo-service .
+
+FROM scratch
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+COPY --from=builder /src/geo-service /
+CMD ["/geo-service"]