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

lib/services/src/power_policy.h

@@ -0,0 +1,47 @@
+#pragma once
+
+#include <cstdint>
+
+namespace roro {
+
+enum class ScreenState : uint8_t { On, Dimmed, Off };
+
+// Screen power from user activity. Services keep running whatever the screen does.
+class PowerPolicy {
+   public:
+    PowerPolicy(uint32_t dimAfterMs, uint32_t offAfterMs) : dimMs_(dimAfterMs), offMs_(offAfterMs) {}
+
+    void setTimeouts(uint32_t dimAfterMs, uint32_t offAfterMs) {
+        dimMs_ = dimAfterMs;
+        offMs_ = offAfterMs;
+    }
+
+    // Records a key press. Returns true if the key only woke an Off screen and must not reach the App.
+    bool activity(uint32_t nowMs);
+
+    ScreenState update(uint32_t nowMs);
+    ScreenState state() const { return state_; }
+
+   private:
+    uint32_t dimMs_;
+    uint32_t offMs_;
+    uint32_t lastActivityMs_ = 0;
+    ScreenState state_ = ScreenState::On;
+};
+
+enum class ButtonAction : uint8_t { None, ShortPress, LongPress };
+
+// G0 button: a long press fires as soon as the hold time is reached (power off); a short press on release.
+class PowerButton {
+   public:
+    explicit PowerButton(uint32_t longPressMs) : longMs_(longPressMs) {}
+    ButtonAction update(bool pressed, uint32_t nowMs);
+
+   private:
+    uint32_t longMs_;
+    bool pressed_ = false;
+    bool longFired_ = false;
+    uint32_t pressedAtMs_ = 0;
+};
+
+}  // namespace roro