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/core/src/event.h

@@ -5,12 +5,14 @@
 
 namespace roro {
 
+enum class NotificationLevel : int32_t { Info, Warning, Message };
+
 // Everything Services announce to the UI. Add new kinds before Count.
 enum class EventType : uint8_t {
     BatteryChanged,    // a = percent, b = millivolts
     Notification,      // text = message, a = NotificationLevel
-    StorageThreshold,  // a = usage percent, b = threshold crossed (80 / 90 / 100)
-    SettingChanged,    // text = setting key
+    StorageThreshold,  // a = usage percent, b = level now in effect (0 / 80 / 90 / 100)
+    SettingChanged,    // a = Setting, text = storage key
     Count
 };