Add M0 services: settings, battery, clock, storage, power

lib/services holds the host-tested logic:
- Settings: typed, validated, persisted, SettingChanged events,
  transmit gated on a confirmed Region
- BatteryEstimator: LiPo curve, median smoothing against TX sags
- ClockModel: source priority GNSS > NTP > mesh, relative ages,
  Europe/Brussels local time via POSIX TZ
- StorageMonitor: warning once per boot at 80%, Logs stop at 90%,
  Captures stop with < 2 MiB left
- PowerPolicy / PowerButton: dim/off timeouts, wake key swallowed only
  when the screen was off, G0 long press

src/services wires them to the hardware (NVS, battery ADC, SD on the
shared SPI bus with the LoRa CS held high, backlight, deep sleep), and
main.cpp is a temporary diagnostics screen for the hardware checks.

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

src/services/clock_service.h

@@ -0,0 +1,38 @@
+#pragma once
+
+#include <Arduino.h>
+
+#include "clock_model.h"
+#include "event_bus.h"
+#include "service.h"
+#include "settings.h"
+
+namespace roro {
+
+// Holds wall-clock time. Sources (GNSS in M2, NTP in M1, mesh in M4) call set().
+class ClockService : public Service {
+   public:
+    ClockService(const Settings& settings, EventBus& bus) : settings_(settings) {
+        bus.subscribe(EventType::SettingChanged, [this](const Event& e) {
+            if (e.a == static_cast<int32_t>(Setting::Timezone)) applyTimezone();
+        });
+    }
+    const char* name() const override { return "clock"; }
+    void start() override { applyTimezone(); }
+
+    bool set(int64_t utcSeconds, TimeSource source) { return model_.set(utcSeconds, source, millis()); }
+    const ClockModel& model() const { return model_; }
+
+    // "14:05" once set; otherwise "--:--".
+    std::string displayTime() const {
+        return model_.isSet() ? ClockModel::formatLocalTime(model_.utcNow(millis())) : "--:--";
+    }
+
+   private:
+    void applyTimezone() { ClockModel::applyTimezone(settings_.getString(Setting::Timezone).c_str()); }
+
+    const Settings& settings_;
+    ClockModel model_;
+};
+
+}  // namespace roro