BUG: Invalid EMBEDDING_MAX_BATCH_SIZE Value Triggers ValueError in backend/config.py

### Is there an existing issue for this?

- [x] I have searched the existing issues

### What happened?

## 📌 Issue Overview
`EMBEDDING_MAX_BATCH_SIZE` Crashes Application if Set to Non-Integer Value

## 🔍 Steps to Reproduce
1. Set the environment variable `EMBEDDING_MAX_BATCH_SIZE` to a non-integer value (e.g., `abc` or leave it empty).
2. Run the application.
3. The application attempts to convert the value to `int` in `backend/config.py`.
4. Show the error.

## 🎯 Expected Behavior
The application should handle invalid or missing `EMBEDDING_MAX_BATCH_SIZE` values gracefully and fall back to a safe default without crashing.

## 🚨 Actual Behavior
If `EMBEDDING_MAX_BATCH_SIZE` is set to a non-integer value or is empty, the application crashes with a `ValueError` in `backend/config.py`.

## 📷 Screenshot

## 💡 Suggested Improvements
- Add error handling in `backend/config.py` to catch invalid `EMBEDDING_MAX_BATCH_SIZE` values.
- Use the default value if parsing fails.

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- [x] I want to work on this issue