Import ESP_UniClock (upstream 1189810)

Vendored from https://github.com/gpeter62/ESP_UniClock: the sketch
source, the web UI and the libraries the ESP8266 build needs, unpacked
from the bundled zips. Adds a PlatformIO project for the ESP-12. The
source is unchanged; local changes follow as separate commits.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

firmware/uniclock/platformio.ini

@@ -0,0 +1,30 @@
+; ESP_UniClock for the RetroModding NixieIN12v2 (5 V) clock. See README.md in this folder.
+;
+; The sketch keeps the upstream Arduino IDE layout (ESP32_UniClock2/ with all .ino files), so it
+; still opens in the Arduino IDE. Libraries are the versions bundled upstream, unpacked in lib/.
+
+[platformio]
+src_dir = ESP32_UniClock2
+data_dir = ESP32_UniClock2/data
+default_envs = nixie_in12
+
+[env:nixie_in12]
+platform = espressif8266
+board = esp12e
+framework = arduino
+; 4 MB flash: 2 MB app slot, 2 MB SPIFFS at 0x200000 (same split as the stock firmware)
+board_build.ldscript = eagle.flash.4m2m.ld
+board_build.filesystem = spiffs
+board_build.flash_mode = dio
+board_build.f_cpu = 80000000L
+; evaluate #ifdefs when resolving includes: the sketch includes ESP32-only libraries inside #if
+lib_ldf_mode = chain+
+; CH340C adapter on COM7 without auto-reset: put the clock in flash mode by hand
+; (hold GPIO0 to GND, tap RST, release GPIO0) before every upload/uploadfs.
+upload_port = COM7
+upload_speed = 460800
+; "ck" = esptool --before no_reset --after soft_reset (no DTR/RTS toggling)
+upload_resetmethod = ck
+monitor_port = COM7
+monitor_speed = 115200
+monitor_filters = esp8266_exception_decoder