M1 step 3: Log writing and Storage Clean-up

- lib/storage_model (host-tested): FAT-safe names, daily Log paths,
  dates from Log/Capture file names, CleanupPlan by category and age,
  byte formatting
- StorageService does all card I/O on its task: queued Log lines are
  written in batches each second (dropped while Logs are paused),
  plus file listing and deletion jobs
- Settings > Storage moves into StoragePage: usage, Clean up
  (category, age with size preview, confirmation), Erase SD card
- Clock: local date for Log names
- Serial: log <text>, sd list

Verified on the device: lines land in /irc/dev/#test/2026-10-02.log
with folders created as needed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

test/test_clock/test_clock.cpp

@@ -61,6 +61,12 @@ void test_local_time_in_brussels_summer_and_winter() {
     TEST_ASSERT_EQUAL_STRING("13:00", ClockModel::formatLocalTime(k2026_01_15_1200Z).c_str());
 }
 
+void test_local_date_in_brussels() {
+    ClockModel::applyTimezone(kBrussels);
+    // 2026-07-01 23:30Z is already July 2nd in Brussels (UTC+2)
+    TEST_ASSERT_EQUAL_STRING("2026-07-02", ClockModel::formatLocalDate(k2026_07_01_1200Z + 11 * 3600 + 1800).c_str());
+}
+
 int main() {
     UNITY_BEGIN();
     RUN_TEST(test_clock_is_unset_until_a_source_sets_it);
@@ -70,5 +76,6 @@ int main() {
     RUN_TEST(test_utc_now_survives_millis_wraparound);
     RUN_TEST(test_relative_age_formatting);
     RUN_TEST(test_local_time_in_brussels_summer_and_winter);
+    RUN_TEST(test_local_date_in_brussels);
     return UNITY_END();
 }