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/README.md

@@ -0,0 +1,24 @@
+# ESP_UniClock for the NixieIN12v2 clock
+
+Firmware for this clock, based on [ESP_UniClock](https://github.com/gpeter62/ESP_UniClock) by
+Peter Gautier (GPL-3.0-or-later), vendored from upstream commit `1189810` (2026-09-07).
+
+- `ESP32_UniClock2/`: the upstream sketch folder (all `.ino`/`.h` files and the web UI in `data/`).
+  It keeps the upstream layout, so it still opens in the Arduino IDE.
+- `lib/`: the library versions bundled upstream (`libraries/*.zip`), only those the ESP8266 build
+  needs. The upstream manuals, datasheets, photos and ESP32-only libraries were left out.
+- `platformio.ini`: PlatformIO build for the ESP-12 (4 MB flash, 2 MB SPIFFS).
+
+Local changes are separate commits on top of the import (`git log -- firmware/uniclock`).
+
+## Build and flash
+
+```sh
+pio run                      # build
+pio run -t upload            # flash the firmware over COM7
+pio run -t uploadfs          # flash the web UI (data/) to SPIFFS
+pio device monitor           # serial log, 115200 Bd
+```
+
+The CH340C adapter has no auto-reset: before each upload, hold GPIO0 to GND, tap RST to GND, then
+release GPIO0. See `CLAUDE.md` in the repo root for the wiring.