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/web/shares_test.go

@@ -59,6 +59,7 @@ func withShareRunner(srv *Server, f *shareRunner) {
 	srv.shm = shares.New(f.run)
 	srv.shm.LookPath = func(string) (string, error) { return "/usr/sbin/x", nil }
 	srv.shm.Owner, srv.shm.UID, srv.shm.GID = "ansible", "1000", "1000"
+	srv.shm.IncludeDir, srv.shm.ExportsDir = "", ""
 }
 
 func TestSharesSMBFlow(t *testing.T) {