Update TODO status, add CAD files and pictures, move USB port to COM18

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

README.md

@@ -305,23 +305,23 @@ The serial protocol is described in [src/nano/README.md](src/nano/README.md).
 
 ## TODO
 
-- [ ] **Install the recovery app** (one-time USB flash, see
+- [X] **Install the recovery app** (one-time USB flash, see
   [One-time installation](#one-time-installation-usb)). Until then the ESP32 runs the old
   flash layout: the clock firmware works, but without the recovery app; the Home
   Assistant sensor shows "no recovery app".
-- [ ] **Test the web UI on the real hardware**: live view, uploading and drawing a bitmap,
+- [X] **Test the web UI on the real hardware**: live view, uploading and drawing a bitmap,
   live mode, choosing a page, settings, Home Assistant settings (restart).
 - [ ] **Test the recovery app on the real hardware**: the Home Assistant button, the setup
   WiFi with a wrong WiFi password, 3 quick power cycles, and an OTA upload into it.
 
-- [ ] **Rewire the Nano link to UART2.** The firmware now uses `Serial2` (GPIO 16/17)
+- [X] **Rewire the Nano link to UART2.** The firmware now uses `Serial2` (GPIO 16/17)
   instead of `Serial` (GPIO 1/3). Move the ESP32 TX wire from GPIO 1 to **GPIO 17** before
   you flash this firmware, or the display gets no data. See
   [Wiring between ESP32 and Nano](#wiring-between-esp32-and-nano).
 - [ ] **Add the reply wire:** Nano D1 (TX) → voltage divider → ESP32 GPIO 16 (RX2). With it,
   the ESP sends the first frame as soon as the Nano is ready, instead of after 3 s, and
   the Nano can be flashed over WiFi (`nano_ota`).
-- [ ] **Test flashing over WiFi on the real hardware.** The uploader is tested against a
+- [X] **Test flashing over WiFi on the real hardware.** The uploader is tested against a
   simulated bootloader, not yet against the real Nano. Check especially that the old
   bootloader starts after the relay power cycle.
 - [ ] **Check the boot timing.** Build the Nano with `MEASURE_REFRESH` to see how long a