BUG: Appointment form modal inputs hidden when keyboard opens on Android

### Is there an existing issue for this?

- [x] I have searched the existing issues

### What happened?

## 📌 Issue Overview
The "Add Appointment" modal form layout breaks when the keyboard opens.
Text inputs become partially hidden and only a small area is visible, making it difficult to enter details.

## 🔍 Steps to Reproduce
1. Open the app
2. Navigate to Calendar screen
3. Tap "+" → Add Appointment
4. Tap any textbox (Title/Description/Location)
5. Keyboard opens
6. Try scrolling

## 🎯 Expected Behavior
- Modal should move up when keyboard opens
- All textboxes should remain fully visible
- User should be able to scroll comfortably

## 🚨 Actual Behavior
- Keyboard overlaps the modal
- Only small portion of form is visible
- Some inputs are hidden
- Hard to scroll and enter details

## 📷 Screenshot

## 💡 Suggested Improvements
Wrap modal content with KeyboardAvoidingView and ScrollView to properly handle keyboard overlap:

### Record

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