docs: add lab18 submission - Nix reproducible builds

labs/lab18/app_python/Dockerfile

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+FROM python:3.12-slim
+
+WORKDIR /app
+
+COPY requirements.txt ./
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY . .
+
+RUN groupadd -g 1000 nonroot \ 
+    && useradd -r --no-create-home -u 1000 -g nonroot nonroot
+
+RUN mkdir -p /data && chown -R nonroot:nonroot /data && chmod 755 /data
+
+USER nonroot
+
+EXPOSE 5000/tcp
+
+ENTRYPOINT ["python", "app.py"]

labs/lab18/app_python/README.md

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+# Overview
+
+Lightweight web application built using __FastAPI__. It provides essential service and system information, along with a health check endpoint to monitor application status. The application shares various details about the server environment, including runtime status and configuration.
+
+## Prerequisites
+
+Before you begin, ensure you have the following prerequisites:
+
+Python Version: Python 3.11 or higher
+Dependencies: The application depends on the FastAPI framework and other packages specified in the requirements.txt file.
+
+## Installation
+
+```bash
+python -m venv venv
+source venv/bin/activate
+pip install -r requirements.txt
+```
+
+## Running the Application
+
+```bash python app.py
+# Or with custom config
+PORT=8080 python app.py
+```
+
+## How to run using Docker
+
+### Build your own docker image
+
+```bash
+cd app_python
+docker build -t <tag> .
+```
+
+### OR pull from Docker Hub
+
+```bash
+docker pull bulatgazizov/app_python:0.0.1
+```
+
+### Run application
+
+```bash
+docker run -p 5000:<expose port> <tag>
+```
+
+## API Endpoints
+
+| Method | Endpoint   | Description                             |
+|--------|------------|-----------------------------------------|
+| GET    | /          | Service and system information.         |
+| GET    | /health    | Health check for the application.       |
+
+### `/` - Service and System Information
+
+This endpoint returns information about the service, system details, and configuration.
+
+### `/health` - Health Check
+
+This endpoint returns the health status of the application along with the current timestamp.
+
+### `/visits`
+
+Return current visits count.
+
+Example:
+
+```json
+{
+    'visits': 43,
+    'timestamp': "YYYY-MM-DD HH:MM:SS.mmmmmm"
+}
+```
+
+## Configuration
+
+| Environment Variable | Description                             | Default Value |
+|----------------------|-----------------------------------------|---------------|
+| `HOST`               | The host address for the application.   | `0.0.0.0`     |
+| `PORT`               | The port the application listens on.    | `5000`        |
+| `DEBUG`              | Enables debug mode if set to `true`.    | `false`       |