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

test/test_clock/test_clock.cpp

@@ -0,0 +1,74 @@
+#include <unity.h>
+
+#include "clock_model.h"
+
+using namespace roro;
+
+void setUp() {}
+void tearDown() {}
+
+static const char* kBrussels = "CET-1CEST,M3.5.0,M10.5.0/3";
+static const int64_t k2026_07_01_1200Z = 1782907200;
+static const int64_t k2026_01_15_1200Z = 1768478400;
+
+void test_clock_is_unset_until_a_source_sets_it() {
+    ClockModel c;
+    TEST_ASSERT_FALSE(c.isSet());
+    TEST_ASSERT_EQUAL(static_cast<int>(TimeSource::None), static_cast<int>(c.source()));
+}
+
+void test_time_advances_with_uptime_after_being_set() {
+    ClockModel c;
+    TEST_ASSERT_TRUE(c.set(k2026_07_01_1200Z, TimeSource::Ntp, 5000));
+    TEST_ASSERT_TRUE(c.isSet());
+    TEST_ASSERT_EQUAL_INT64(k2026_07_01_1200Z + 10, c.utcNow(15000));
+}
+
+void test_lower_priority_source_does_not_override() {
+    ClockModel c;
+    c.set(k2026_07_01_1200Z, TimeSource::Ntp, 0);
+    TEST_ASSERT_FALSE(c.set(k2026_07_01_1200Z + 500, TimeSource::Mesh, 0));
+    TEST_ASSERT_EQUAL_INT64(k2026_07_01_1200Z, c.utcNow(0));
+}
+
+void test_equal_or_higher_priority_source_overrides() {
+    ClockModel c;
+    c.set(k2026_07_01_1200Z, TimeSource::Mesh, 0);
+    TEST_ASSERT_TRUE(c.set(k2026_07_01_1200Z + 1, TimeSource::Mesh, 0));
+    TEST_ASSERT_TRUE(c.set(k2026_07_01_1200Z + 2, TimeSource::Gnss, 0));
+    TEST_ASSERT_EQUAL(static_cast<int>(TimeSource::Gnss), static_cast<int>(c.source()));
+}
+
+void test_utc_now_survives_millis_wraparound() {
+    ClockModel c;
+    c.set(k2026_07_01_1200Z, TimeSource::Ntp, 0xFFFFFFFFu - 999);
+    TEST_ASSERT_EQUAL_INT64(k2026_07_01_1200Z + 2, c.utcNow(1000));
+}
+
+void test_relative_age_formatting() {
+    TEST_ASSERT_EQUAL_STRING("now", ClockModel::formatAge(0).c_str());
+    TEST_ASSERT_EQUAL_STRING("now", ClockModel::formatAge(59).c_str());
+    TEST_ASSERT_EQUAL_STRING("1 min ago", ClockModel::formatAge(60).c_str());
+    TEST_ASSERT_EQUAL_STRING("59 min ago", ClockModel::formatAge(3599).c_str());
+    TEST_ASSERT_EQUAL_STRING("1 h ago", ClockModel::formatAge(3600).c_str());
+    TEST_ASSERT_EQUAL_STRING("23 h ago", ClockModel::formatAge(86399).c_str());
+    TEST_ASSERT_EQUAL_STRING("2 d ago", ClockModel::formatAge(2 * 86400).c_str());
+}
+
+void test_local_time_in_brussels_summer_and_winter() {
+    ClockModel::applyTimezone(kBrussels);
+    TEST_ASSERT_EQUAL_STRING("14:00", ClockModel::formatLocalTime(k2026_07_01_1200Z).c_str());
+    TEST_ASSERT_EQUAL_STRING("13:00", ClockModel::formatLocalTime(k2026_01_15_1200Z).c_str());
+}
+
+int main() {
+    UNITY_BEGIN();
+    RUN_TEST(test_clock_is_unset_until_a_source_sets_it);
+    RUN_TEST(test_time_advances_with_uptime_after_being_set);
+    RUN_TEST(test_lower_priority_source_does_not_override);
+    RUN_TEST(test_equal_or_higher_priority_source_overrides);
+    RUN_TEST(test_utc_now_survives_millis_wraparound);
+    RUN_TEST(test_relative_age_formatting);
+    RUN_TEST(test_local_time_in_brussels_summer_and_winter);
+    return UNITY_END();
+}