Stop IRC by hand; remove mDNS

IrcService::disconnect() stops the session from any state: QUIT if
connected, then no more retries. /quit goes through it (before, it only
stopped a connected session; while waiting for Wi-Fi or retrying it did
nothing), and so does the new `irc stop` command. Stopped by hand,
opening the IRC App no longer reconnects; typing a line does.

mDNS is gone: it never crossed the dev box's routed network, and it
cost about 7.5 KB of RAM. Pushes go to the IP shown in Settings ->
Firmware, which drops its Name row. OTA Q54 records the change.

On the device, Debug Build: 105.6 KB free with Wi-Fi (was 98); with IRC
on TLS 54 KB free (was 46); after `irc stop`, back to 99 KB.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

src/services/update_service.cpp

@@ -1,13 +1,11 @@
 #include "update_service.h"
 
-#include <ESPmDNS.h>
 #include <SD.h>
 #include <WiFi.h>
 #include <esp_ota_ops.h>
 
 #include <memory>
 
-#include "platform/identity.h"
 #include "platform/ota_device.h"
 #include "platform/system_info.h"
 #include "probation.h"
@@ -66,7 +64,6 @@ class FileSource : public UpdateSource {
 UpdateService::UpdateService(KeyValueStore& store, WifiService& wifi, SavedNetworks& saved, StorageService& storage,
                              EventBus& bus, const Settings& settings)
     : store_(store), wifi_(wifi), saved_(saved), storage_(storage), bus_(bus), settings_(settings) {
-    hostname_ = "roro9stack-" + identity::defaultShortName();
 }
 
 void UpdateService::notify(const std::string& text, NotificationLevel level) {
@@ -196,11 +193,9 @@ void UpdateService::listen() {
         bool connected = wifi_.state() == WifiController::State::Connected;
         if (connected && !listening) {
             server.begin();
-            if (MDNS.begin(hostname_.c_str())) MDNS.addService("roro9stack", "tcp", kPort);
             listening = true;
         } else if (!connected && listening) {
             server.end();
-            MDNS.end();
             listening = false;
         }
         // The main loop restarts into an installed update when it's safe. If it never does (stuck,