Shares of other services and RepoISO integration

- include SMB drop-ins from /etc/samba/smb.conf.d into the generated smb.conf
- keep smbd/nfs-server running while other services (/etc/exports.d, drop-ins) share,
  instead of disabling them when nasmon has no shares of its own
- list those shares read-only on /shares
- settings: RepoISO URL; poll its /api/integration/status, dashboard card, menu link,
  alerts for portal down, stale worker, failed jobs, unmounted publications

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/collect/repoiso_test.go

@@ -0,0 +1,29 @@
+package collect
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestFetchRepoISO(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/api/integration/status" {
+			http.NotFound(w, r)
+			return
+		}
+		_, _ = w.Write([]byte(`{"version":"0.1.3","worker_alive":true,"images":5,"images_bytes":1024,"jobs_failed_24h":1}`))
+	}))
+	defer srv.Close()
+	r := FetchRepoISO(srv.URL + "/")
+	if !r.Reachable || r.Version != "0.1.3" || !r.WorkerAlive || r.Images != 5 || r.JobsFailed24h != 1 || r.URL != srv.URL {
+		t.Fatalf("unexpected %+v", r)
+	}
+	if r := FetchRepoISO(srv.URL + "/missing"); r.Reachable || r.Error != "HTTP 404" {
+		t.Fatalf("404 not reported: %+v", r)
+	}
+	srv.Close()
+	if r := FetchRepoISO(srv.URL); r.Reachable || r.Error == "" {
+		t.Fatalf("closed server reported reachable: %+v", r)
+	}
+}