M1 step 2: Wi-Fi Service, Saved Networks, NTP, Settings page

- lib/wifi (host-tested): SavedNetworks (up to 8, validated, hidden
  flag, persisted) and WifiController (joins the strongest Saved
  Network, tries hidden ones in turn, backoff 10/30/60 s, connect
  timeout, Monitoring override, radio off without Saved Networks)
- WifiService carries out the controller's actions, sets the EU
  country code, and syncs the Clock over SNTP without touching the TZ
- Wi-Fi On/Off setting; Settings > Wi-Fi page: status, add from a scan
  or a hidden network, forget
- Status Bar: W + signal bars, W? while searching, MON while monitoring
- Serial: wifi add / wifi status (replaces the step 1 heap probe)

Verified on the device: joins the test network ~5 s after boot, clock
set over NTP, ~129 KB free heap while connected.

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

lib/apps_model/src/settings_menu.cpp

@@ -20,7 +20,8 @@ const RowDef kRows[] = {
     {Row::Region, Kind::Choice, "Region"},      {Row::Timezone, Kind::Choice, "Timezone"},
     {Row::Brightness, Kind::Slider, "Brightness"}, {Row::DimTimeout, Kind::Choice, "Dim after"},
     {Row::OffTimeout, Kind::Choice, "Screen off after"}, {Row::Sound, Kind::Toggle, "Sound & LED"},
-    {Row::ProbeMacs, Kind::Toggle, "Probe MACs"}, {Row::Storage, Kind::Page, "Storage"},
+    {Row::ProbeMacs, Kind::Toggle, "Probe MACs"}, {Row::Wifi, Kind::Page, "Wi-Fi"},
+    {Row::Storage, Kind::Page, "Storage"},
     {Row::About, Kind::Page, "About"},
 };
 
@@ -78,6 +79,7 @@ std::string SettingsMenu::value(int i) const {
         case Row::OffTimeout: return formatSeconds(settings_.getInt(Setting::OffTimeoutS));
         case Row::Sound: return settings_.getBool(Setting::Sound) ? "On" : "Off";
         case Row::ProbeMacs: return settings_.getBool(Setting::ProbeMacRaw) ? "Raw" : "Pseudonymised";
+        case Row::Wifi: return settings_.getBool(Setting::WifiEnabled) ? "On" : "Off";
         default: return "";
     }
 }