Implement code quality improvements from PR #3 review

## Summary
Follow-up issue to implement the code quality improvements suggested in the [PR #3 code review](https://github.com/dankirichok1/exampleproject/pull/3#discussion_r2288668405) that won't be addressed in the current merge request.

## Background
PR #3 successfully implements the multiple variable functionality, but the code review identified several opportunities for improvement to follow Java best practices and enhance maintainability.

## Suggested Improvements from Code Review

### 1. 🔄 **Replace repetitive print statements with loops**
**Current:**
```java
System.out.println("Hello World");
System.out.println("Hello World");
System.out.println("Hello World");
System.out.println("Hello World");
System.out.println("Hello World");
System.out.println("Hello World");
```

**Suggested:**
```java
for (int count = 0; count < 6; count++) {
System.out.println("Hello World");
}
```

### 2. 💡 **Add named constants for magic numbers**
**Suggested:**
```java
private static final int BASE_VALUE = 123;
private static final int VARIABLE_COUNT = 10;
private static final int GREETING_COUNT = 6;
```

### 3. 📊 **Consider using arrays for multiple variables**
**Suggested:**
```java
int[] numbers = new int[10];
Arrays.fill(numbers, 123);
int sum = Arrays.stream(numbers).sum();
```

### 4. 📖 **Add comprehensive JavaDoc documentation**
**Suggested:**
```java
/**
* Enhanced HelloWorld program demonstrating multiple variable addition
* and repeated output functionality.
*
* @author dankirichok1
* @version 2.0 - Enhanced with multiple variables
*/
```

### 5. 🎯 **Optimize sum calculation**
**Suggested:**
```java
// More efficient approach
int sum = BASE_VALUE * VARIABLE_COUNT; // 123 * 10 = 1230
```

## Acceptance Criteria
- [ ] Replace repeated print statements with a loop
- [ ] Add named constants for magic numbers (123, 10, 6)
- [ ] Add comprehensive JavaDoc documentation
- [ ] Consider refactoring to use arrays (optional)
- [ ] Optimize sum calculation or add explanatory comments
- [ ] Maintain existing functionality and output
- [ ] Code passes compilation and produces same result (1230)

## Expected Benefits
- **Maintainability:** Easier to modify greeting count and variable values
- **Readability:** Clear constants and documentation
- **Performance:** Optimized calculations
- **Best Practices:** Follows Java coding standards

## Related
- Addresses code review feedback from [PR #3](https://github.com/dankirichok1/exampleproject/pull/3)
- Follow-up to [Issue #2](https://github.com/dankirichok1/exampleproject/issues/2)
- Part of ongoing code quality improvements