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/services/wifi_service.h

@@ -0,0 +1,62 @@
+#pragma once
+
+#include <vector>
+
+#include "event_bus.h"
+#include "saved_networks.h"
+#include "service.h"
+#include "services/clock_service.h"
+#include "settings.h"
+#include "wifi_controller.h"
+
+namespace roro {
+
+struct ScanEntry {
+    std::string ssid;
+    int rssi;
+    bool open;
+};
+
+// Owns the Wi-Fi radio: carries out the WifiController's decisions with the ESP32 Wi-Fi stack,
+// syncs the clock over NTP once Connected, and runs scans for the Settings network list.
+class WifiService : public Service {
+   public:
+    WifiService(Settings& settings, SavedNetworks& saved, ClockService& clock)
+        : settings_(settings), saved_(saved), clock_(clock), controller_(saved) {}
+    const char* name() const override { return "wifi"; }
+    uint32_t tickIntervalMs() const override { return 250; }
+    void tick(uint32_t nowMs) override;
+
+    WifiController::State state() const { return controller_.state(); }
+    const std::string& ssid() const { return controller_.ssid(); }
+    int rssi() const;
+
+    // Scan for the "add a network" list; results arrive in listScan() when listScanDone().
+    void startListScan();
+    bool listScanDone() const { return !listScanPending_; }
+    const std::vector<ScanEntry>& listScan() const { return listScan_; }
+
+    // A Saved Network was added: try it now rather than after the retry delay.
+    void savedNetworksChanged() { controller_.retryNow(millis()); }
+
+    void requestMonitor() { apply(controller_.requestMonitor()); }
+    void releaseMonitor() { apply(controller_.releaseMonitor(settings_.getBool(Setting::WifiEnabled))); }
+
+   private:
+    void apply(const WifiController::Step& step);
+    void startScan();
+    void finishScan(uint32_t nowMs);
+    void startNtp();
+
+    Settings& settings_;
+    SavedNetworks& saved_;
+    ClockService& clock_;
+    WifiController controller_;
+    bool scanRunning_ = false;
+    bool listScanPending_ = false;
+    std::vector<ScanEntry> listScan_;
+    bool ntpWaiting_ = false;
+    bool radioInitialised_ = false;
+};
+
+}  // namespace roro