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/alert/repoiso_test.go

@@ -0,0 +1,35 @@
+package alert
+
+import (
+	"testing"
+	"time"
+
+	"nasmon/internal/collect"
+)
+
+func TestRepoISORules(t *testing.T) {
+	base := Input{Now: time.Now()}
+	if ev := Evaluate(base); len(ev) != 0 {
+		t.Fatalf("integration off must not alert: %v", keys(ev))
+	}
+
+	in := base
+	in.RepoISO = &collect.RepoISO{URL: "http://127.0.0.1", Error: "connection refused"}
+	ev := Evaluate(in)
+	if !has(ev, "repoiso:api:down") || len(ev) != 1 || ev[0].Level != LevelCrit {
+		t.Fatalf("down: %v", keys(ev))
+	}
+
+	in.RepoISO = &collect.RepoISO{Reachable: true, WorkerAlive: false, JobsFailed24h: 2, PublicationsError: 1}
+	ev = Evaluate(in)
+	for _, k := range []string{"repoiso:worker:stale", "repoiso:jobs:failed", "repoiso:publications:error"} {
+		if !has(ev, k) {
+			t.Errorf("missing %s in %v", k, keys(ev))
+		}
+	}
+
+	in.RepoISO = &collect.RepoISO{Reachable: true, WorkerAlive: true}
+	if ev = Evaluate(in); len(ev) != 0 {
+		t.Fatalf("healthy RepoISO alerted: %v", keys(ev))
+	}
+}