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/shares/render.go

@@ -26,8 +26,9 @@ func anyGuest(c Config) bool {
 
 // RenderSMB produces the complete smb.conf. owner is the Unix account every
 // SMB session acts as (force user), so files end up with the same owner the
-// containers use.
-func RenderSMB(c Config, owner string) string {
+// containers use. includes are drop-in files of other services appended as
+// "include =" lines.
+func RenderSMB(c Config, owner string, includes ...string) string {
 	var b strings.Builder
 	fmt.Fprintf(&b, "%s\n\n[global]\n", Header)
 	// Bad User turns unknown accounts (e.g. the Windows login) into guests.
@@ -98,6 +99,12 @@ func RenderSMB(c Config, owner string) string {
 			fmt.Fprintf(&b, "   %s\n", l)
 		}
 	}
+	if len(includes) > 0 {
+		b.WriteString("\n# Shares of other services (read-only in nasmon)\n")
+		for _, f := range includes {
+			fmt.Fprintf(&b, "include = %s\n", f)
+		}
+	}
 	return b.String()
 }