Adds CLOCK_90 and the nixie595.ino driver: two 74HC595s on hardware
SPI (GPIO13/14, latch GPIO15), multiplexed from an IRAM-only timer1
ISR. Neon dots on P1; P2 is the decimal-point line on this board.
Also:
- NeoPixel on any ESP8266 pin via bit-bang (GPIO12), and take the pin
back after SPI.begin() claimed it as MISO
- ArduinoOTA (USE_ARDUINO_OTA), with an OTA upload env in platformio.ini
- DST: EU end date (last Sunday of October) instead of the first Sunday
of November, and recompute the time from the rules when DST is
toggled instead of shifting it by 1 h
- forward declarations so PlatformIO's .ino conversion compiles
- FIRMWARE_SERVER can be overridden; empty for CLOCK_90
Verified on the clock: tubes, order, dots, LEDs, LDR, NTP time with DST.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
