FEATURE REQUEST: Creator Profile Data Preprocessing Utility for AI Modules

### Is your feature request related to a problem?

- [x] Yes, it is related to a problem

### Describe the feature you'd like

## 🌟 Feature Description
Add a reusable backend utility module for **creator profile data preprocessing**, to support AI-powered features like sentiment analysis, niche extraction, and sponsorship pricing. The module will clean and normalize creator input data into structured formats suitable for downstream AI processing.

## 🔍 Problem Statement
Currently, InPactAI has several planned AI components (e.g., #11, #13, #22), but no unified preprocessing step for creator data. Without a standard pipeline, data inputs may be inconsistent, reducing model accuracy and reusability across features.

This feature will solve the problem by introducing a centralized utility that prepares creator data for AI modules, improving code modularity and scalability.

## 🎯 Expected Outcome
- A new file `creator_preprocessor.py` under `Backend/app/ai/` (or appropriate path)
- Functions to:
- Normalize text (e.g., bios, content descriptions)
- Extract hashtags, emojis, keyword frequency
- Calculate engagement rate and structure numerical features
- Optional: Include unit tests and test input mockups
- Utility ready to be imported in upcoming AI modules

## 📷 Screenshots and Design Ideas
No UI changes. Design idea involves modular, testable functions returning dictionaries or JSON-ready structures. Example:

```python
{
"bio_clean": "travel lover food reviewer",
"hashtags": ["#foodie", "#wanderlust"],
"emoji_count": 3,
"engagement_rate": 0.067,
"word_count": 14
}
```

### Record

- [x] I agree to follow this project's Code of Conduct
- [x] I want to work on implementing this feature