Previously every successful config save triggered ESP.restart() — meant rapid
config changes caused reboot cascades and made the test suite unable to run
multiple cases against /config. Now restarts only if ssid/password/hostname/
ntp_server changed; other settings (brightness, timezone, intervals, coords,
display options) apply live without reboot.
tests/test_device.py: fixed expected field names for /api/time
(time/hours/minutes/epoch instead of current/timezone_offset/ntp_synced).
Test suite: 73/73 passing on hardware. Heap drift <1KB across full fuzz run.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
