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

src/ui/widgets.cpp

@@ -32,6 +32,21 @@ void statusBar(Canvas& c, const StatusInfo& info) {
     if (info.batteryPercent >= 0)
         right(std::to_string(info.batteryPercent) + "%", info.batteryPercent <= 15 ? kWarning : kText);
     if (info.sdPresent) right("SD", info.sdLevel >= 80 ? kWarning : kMuted);
+    switch (info.wifi) {
+        case StatusInfo::Wifi::Connected: {
+            // Three signal bars, then the label.
+            for (int i = 0; i < 3; i++) {
+                int h = 2 + 2 * i;
+                c.fillRect(x - 10 + 4 * i, 9 - h, 3, h, i < info.wifiBars ? kText : kMuted);
+            }
+            x -= 14;
+            right("W", kText);
+            break;
+        }
+        case StatusInfo::Wifi::Searching: right("W?", kMuted); break;
+        case StatusInfo::Wifi::Monitoring: right("MON", kAccent); break;
+        case StatusInfo::Wifi::None: break;
+    }
     if (info.compose) right(std::string("opt ") + (info.compose == '*' ? "" : std::string(1, info.compose)), kAccent);
     c.setTextDatum(top_left);
 }