fix: couple go.mod and base container image version (#188)

I accidentally changed the `go.mod` Go version to 1.25.0 without
changing the base container image's Go version. I coupled both together
in this patch.

Amp-Thread:
https://ampcode.com/threads/T-019cdacf-480d-70ba-8bec-36522b526cbd

Author: sudomateo

Makefile

@@ -1,5 +1,6 @@
 VERSION ?= v0.3.0
-GO_CONTAINER_IMAGE ?= docker.io/golang:1.25.3
+GO_VERSION := $(shell go list -m -f '{{.GoVersion}}')
+GO_CONTAINER_IMAGE ?= docker.io/golang:$(GO_VERSION)
 
 # Set this to non-empty when building and pushing a release.
 RELEASE ?=

go.mod

@@ -1,6 +1,6 @@
 module github.com/oxidecomputer/oxide-cloud-controller-manager
 
-go 1.25.0
+go 1.25.3
 
 require (
 	github.com/google/uuid v1.6.0

tools/go.mod

@@ -1,6 +1,6 @@
 module tools
 
-go 1.25.0
+go 1.25.3
 
 tool helm.sh/helm/v4/cmd/helm