Arduino off-ramp: raw NVS settings reads + millis/delay shim

[zjwhitehead]

Two scoped Arduino off-ramp steps. Does not bump espressif32 / ESP-IDF, does not drop framework = arduino, espidf, and does not migrate GPIO, ADC, LEDC, Wire/SPI, Adafruit, or NimBLE.

1) Finish NVS for device settings (drop Preferences reads)

writeDeviceData() already used raw ESP-IDF nvs_* with a single nvs_commit(). refreshDeviceData() and factory reset still went through Arduino Preferences.

This PR ports the read/load and reset paths to the same raw NVS API and key layout, then removes #include <Preferences.h> and the Preferences instance from device_settings.cpp. Load sites call nvs_get_* / nvs_erase_all directly (no typed getter wrappers).

Field compatibility

Verified against Arduino-ESP32 2.0.17 Preferences.cpp (espressif32@6.13.0) and the existing write-path comments. Keys and NVS types are unchanged, so devices already in the field keep their stored values:

Key	Type	Notes
ver_major, ver_minor, scr_rot, perf_mode, theme, revision	u8	getUChar → nvs_get_u8
metric_tmp, metric_alt	u8 0/1	getBool is getUChar == 1
sea_pres	4-byte blob	getFloat/putFloat are getBytes/putBytes → nvs_*_blob
armed_time	u16	getUShort → nvs_get_u16
tz_offset	i32	getInt → nvs_get_i32

Namespace remains openppg. Missing keys still fall back to the same defaults. Factory reset still wipes the namespace (nvs_erase_all + commit, equivalent to Preferences.clear()) and writes defaults. USBSerial / WebSerial strings and command behavior are unchanged.

2) Time shim: replace Arduino millis() / delay()

Added inc/sp140/time_utils.h:

• timeMillis() → esp_timer_get_time() / 1000ULL, returns unsigned long (same as Arduino millis())
• timeDelay(ms) → vTaskDelay(pdMS_TO_TICKS(ms)) (same as Arduino-ESP32 2.0.17 delay(), which is vTaskDelay(ms / portTICK_PERIOD_MS) with no busy-wait remainder)

On this firmware CONFIG_FREERTOS_HZ=1000, so one tick is 1 ms. Production src/ call sites now use the shim, including BLE files that only needed a clock (NimBLE itself is untouched). Arduino.h includes that are still needed for other APIs are left in place.

Native / screenshot tests keep compiling: the header’s non-ESP_PLATFORM path delegates to the existing Arduino stub millis() / delay() so screenshot timestamps stay on the same clock.

How to test

platformio test -e native-test
platformio run -e OpenPPG-CESP32S3-CAN-SP140

Optional (CI also runs this): ./test/test_screenshots/build_and_run.sh

Validation so far

• platformio test -e native-test: 60/60 passed (local)
• cpplint on inc/ and src/: clean (local)
• First CI pio-build failed on -Werror=format (%lu vs uint32_t). Fixed by returning unsigned long from timeMillis().
• Local full firmware build cannot fetch private openppg/SINE-ESC-CAN; CI pio-build is the equivalent check.

Intentionally left

• src/sp140/diagnostics.cpp still uses Arduino Preferences — boot-diag history lives in a different namespace and is out of scope.
• BLE log strings that say “saved to Preferences” — USB/BLE wording only; settings I/O is already writeDeviceData().
• millis() / delay() in test/native_stubs and test/screenshot_stubs — native clock for unit/screenshot tests.
• millis() in test/test_screenshots — test harness, not firmware.
• Comments in relay headers that mention not calling delay().
• Third-party / Adafruit / NimBLE internals — out of scope.
• Arduino.h includes still required for Serial, GPIO, and other Arduino APIs.

Do not merge until reviewed.