feat: Initialize backend with NestJS framework and serial communication

- Added package.json for backend dependencies and scripts.
- Implemented basic AppController and AppService with a simple "Hello World!" endpoint.
- Created SerialModule for handling serial communication with the Pico.
- Developed SerialController and SerialService to manage serial ports and commands.
- Implemented event streaming for serial data.
- Added Jest tests for AppController and e2e tests for the application.
- Set up TypeScript configuration for the backend.
- Created frontend SendBox component for sending commands to the backend.
- Established Pico firmware for controlling a stepper motor via serial commands.
- Documented project structure and usage in README files.

pico/README_PICO_SERIAL.md

@@ -0,0 +1,35 @@
+# Pico Serial Motor Control Integration
+
+This project enables a Raspberry Pi Pico to be controlled via serial commands from a TypeScript backend. The Pico firmware parses commands received over serial and controls a stepper motor accordingly, while also sending log/status messages back.
+
+## Serial Commands Supported
+- `STEP <steps> <direction>`: Move the motor by the specified number of steps. Direction: 1 for forward, 0 for reverse.
+- `SPEED <delay_us>`: Set the motor speed (delay in microseconds between steps).
+- `LOG <message>`: Print a log message to serial.
+
+## Firmware Files
+- `src/main.cpp`: Main firmware logic, serial command parsing, motor control, logging.
+- `src/ULN2003Stepper.h`, `src/Stepper.h`: Stepper motor driver classes.
+
+## How to Extend
+- Add new serial commands by updating the parser in `main.cpp`.
+- Implement additional motor features or logging as needed.
+- Ensure any new global variables are only defined in one source file, and declared as `extern` elsewhere.
+
+## TypeScript Backend
+- Use a library like `serialport` to communicate with the Pico.
+- Send commands as plain text terminated by `\n`.
+- Read and process log/status messages from serial.
+
+## Example Serial Session
+```
+SPEED 3000
+STEP 4096 1
+LOG Motor moved
+```
+
+## Build & Upload
+Use PlatformIO to build and upload the firmware to the Pico.
+
+---
+This README is intended for another developer or Copilot to implement further changes or features.