Fixes last item size when ExpandableCarousel has no padsEnds

[Zigotote]

Pull Request Checklist

What does this PR do?

Fixes bugs or issues #48

When last item of ExpandableCarousel is bigger than others and padsEnds is false, its bottom is clipped.

That's because 2 carousel items are displayed in the same page, and real page index is floored. So when I switch to slide 4, pageIndex is 3.75 (or 3.xxx, depending on viewportFraction, padding etc etc). And (3.75).floor() is 3, so if the 3rd item is smaller than the 4th, the 4th is displayed but its size is not large enough.

I hope this is clear. You can reproduce with this options in your ExpandableCarousel example :

ExpandableCarouselOptions(
  // viewportFraction: 1.0,
 // enableInfiniteScroll: true, // Remove enabledInfiniteScroll because it makes slide 1 and 4 appear on the same page, so slide 4 sticks to the left of the page and realIndex is correct 
  // enlargeCenterPage: true,
  // initialPage: 1,
  autoPlay: true,
  controller: _controller,
  //showIndicator: false,
  floatingIndicator: false,
  padEnds: false, // Add padEnds
  restorationId: 'expandable_carousel',
)

Checklist

Code Changes

• I have added new features to the package (e.g., autoplay, indicator customization, etc.)
• I have fixed existing issues (e.g., performance, edge cases)
• I have improved the overall structure or optimized the codebase

Documentation

• I have updated the README file or relevant documentation with the changes
• I have added code usage examples or updated existing examples to reflect changes
• I have updated the package version in the pubspec.yaml file

Testing

General Tests

• The carousel widget works correctly with default settings
• The carousel can handle a dynamic number of children (images, texts, etc.)
• The carousel supports custom widgets for carousel items

Autoplay Feature

• Autoplay starts when enabled and stops when disabled
• Autoplay pauses when the user interacts (swipes/taps) with the carousel
• Autoplay resumes after interaction

Indicators and Customization

• The carousel displays indicators correctly and updates when navigating through slides
• Custom indicators (colors, shapes, positions) are rendered correctly
• Custom animations or transitions between slides work as expected

Looping and Scrolling

• Infinite loop mode works smoothly without any jumps or glitches
• The carousel scrolls smoothly horizontally and/or vertically
• Pagination and snapping behavior works as expected

Accessibility

• The carousel widget supports screen readers (e.g., Semantics labels added)
• Users can navigate between items using a keyboard (if necessary)

Responsiveness

• The carousel adapts to different screen sizes (mobile, tablet, desktop)
• The carousel responds correctly to device orientation changes

Error Handling

• The carousel handles empty/null items gracefully
• The carousel handles large data sets without crashes or performance drops

Performance

• I ran performance tests to ensure no regressions
• The carousel renders efficiently, even with a large number of items

How did you verify your code works?

• I ran manual tests to check various carousel configurations (autoplay, infinite loop, custom widgets)
• All tests pass locally (flutter test)

[nixrajput]

Looking fine to be merged.
I will test and merge it soon.

Thank you for the PR.