The Go base has to be 1.26: the NATS client requires it

`nats.go v1.54.0` declares `go >= 1.26`, so `go mod tidy` puts the directive at
1.26.0 and will not leave it at 1.25. The base image is pinned by digest at
1.25.14-alpine, so nothing in this repository compiles against it — caught when the
build machine's own build failed with "go.mod requires go >= 1.26.0 (running go
1.25.14)".

Moved to 1.26.8-alpine by digest, same flavour as before. The pin stays a digest:
the point of pinning is that the compiler does not change underneath a build, and
that is still true one version along.

Two other manifests carry the same pin for the same reason — they compile this
repository's code — and move with it in the catalogue.

module.json

@@ -82,7 +82,7 @@
     "on": [
       {
         "arg": "GO_BASE",
-        "image": "golang@sha256:1ae0735f00daffa3aaf1363a5184c0d2dc55c78e3db4ec70241cdac97bf84b59"
+        "image": "golang@sha256:8ac98ca534ac3f51e1f420a1dd2c15e74c75cfa0f23f3ad27eb5d7236c349a0c"
       }
     ]
   }