Week 14: Flask / serial LED application

This package restores the LED-control source already embedded in my Week 14 page.
The previous Arduino download mistakenly contained a servo sketch.

Layout:
  app.py
  requirements.txt
  templates/index.html
  Arduinocodweek14/Arduinocodweek14.ino

Create a Python virtual environment and install requirements.txt.
Upload Arduinocodweek14.ino using the board package matching your hardware.
The documented LED is on D1. Confirm this against your fabricated board.
Close Arduino Serial Monitor before opening the serial port in Flask.
Set LED_SERIAL_PORT to the actual device port (the historical example is COM10).
Run python app.py from this folder and open http://127.0.0.1:5000/.
Both the firmware and the app use 9600 baud and newline-terminated ON/OFF messages.

Windows PowerShell example:
  python -m venv .venv
  .\.venv\Scripts\Activate.ps1
  python -m pip install -r requirements.txt
  $env:LED_SERIAL_PORT = 'COM10'
  python app.py

macOS/Linux example:
  python3 -m venv .venv
  source .venv/bin/activate
  python -m pip install -r requirements.txt
  LED_SERIAL_PORT=/dev/your-board-port python app.py

The environment variable and corrected template layout are documentation-repair
changes. Hardware operation must still be verified against the actual board.
Package versions used in the original hardware demonstration were not recorded.