Set Up Linters and Code Style Checkers

Introduce basic code quality tools for both Java and Python code in the repo. This helps ensure formatting and best practices are followed consistently across contributors.

### ✅ Tasks

> You don’t need to do all of them in one go — even completing just **one** is helpful!

#### 0️⃣ Java Linter & Formatter
- [ ] Add **Checkstyle** using the default or Google style in `pom.xml` or `build.gradle`
- [ ] Add config file (e.g., `checkstyle.xml`)
- [ ] Add GitHub Action to run `mvn checkstyle:check` or `gradle check`

#### 1️⃣ Java Auto-Formatter
- [ ] Add **Spotless** (Google Java Format) via Gradle or Maven
- [ ] Add commands like `./gradlew spotlessApply` or `mvn spotless:apply`

#### 2️⃣ Python Formatter (for auxiliary Python scripts)
- [ ] Add **Black** formatter (`black .`)
- [ ] Add a GitHub Action to check formatting, e.g.:

```yaml
name: Python Format Check

on: [push, pull_request]

jobs:
black-check:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v3
- name: Install Black
run: pip install black
- name: Check formatting with Black
run: black --check .
3️⃣ .editorconfig