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.cpp

@@ -0,0 +1,36 @@
+#include "power_policy.h"
+
+namespace roro {
+
+bool PowerPolicy::activity(uint32_t nowMs) {
+    bool swallow = state_ == ScreenState::Off;
+    lastActivityMs_ = nowMs;
+    state_ = ScreenState::On;
+    return swallow;
+}
+
+ScreenState PowerPolicy::update(uint32_t nowMs) {
+    uint32_t idle = nowMs - lastActivityMs_;
+    state_ = idle >= offMs_ ? ScreenState::Off : idle >= dimMs_ ? ScreenState::Dimmed : ScreenState::On;
+    return state_;
+}
+
+ButtonAction PowerButton::update(bool pressed, uint32_t nowMs) {
+    if (pressed && !pressed_) {
+        pressed_ = true;
+        longFired_ = false;
+        pressedAtMs_ = nowMs;
+        return ButtonAction::None;
+    }
+    if (pressed && !longFired_ && nowMs - pressedAtMs_ >= longMs_) {
+        longFired_ = true;
+        return ButtonAction::LongPress;
+    }
+    if (!pressed && pressed_) {
+        pressed_ = false;
+        return longFired_ ? ButtonAction::None : ButtonAction::ShortPress;
+    }
+    return ButtonAction::None;
+}
+
+}  // namespace roro