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/clock_model.cpp

@@ -0,0 +1,49 @@
+#include "clock_model.h"
+
+#include <cstdio>
+#include <cstdlib>
+#include <ctime>
+
+namespace roro {
+
+bool ClockModel::set(int64_t utcSeconds, TimeSource source, uint32_t nowMs) {
+    if (source < source_) return false;
+    source_ = source;
+    utcAtSet_ = utcSeconds;
+    msAtSet_ = nowMs;
+    return true;
+}
+
+int64_t ClockModel::utcNow(uint32_t nowMs) const {
+    // Unsigned subtraction handles the millis() wraparound. Uptime beyond 49 days between two
+    // sets would lose 49 days; sources refresh far more often than that.
+    return utcAtSet_ + static_cast<int64_t>(static_cast<uint32_t>(nowMs - msAtSet_) / 1000);
+}
+
+void ClockModel::applyTimezone(const char* posixTz) {
+    setenv("TZ", posixTz, 1);
+    tzset();
+}
+
+std::string ClockModel::formatLocalTime(int64_t utcSeconds) {
+    time_t t = static_cast<time_t>(utcSeconds);
+    struct tm local;
+    localtime_r(&t, &local);
+    char buf[8];
+    std::snprintf(buf, sizeof(buf), "%02d:%02d", local.tm_hour, local.tm_min);
+    return buf;
+}
+
+std::string ClockModel::formatAge(int64_t seconds) {
+    char buf[24];
+    if (seconds < 60) return "now";
+    if (seconds < 3600)
+        std::snprintf(buf, sizeof(buf), "%d min ago", static_cast<int>(seconds / 60));
+    else if (seconds < 86400)
+        std::snprintf(buf, sizeof(buf), "%d h ago", static_cast<int>(seconds / 3600));
+    else
+        std::snprintf(buf, sizeof(buf), "%d d ago", static_cast<int>(seconds / 86400));
+    return buf;
+}
+
+}  // namespace roro