feat(listview): add support for scroll direction in ListView

[usmanvrtx]

Description

Adds configurable scroll direction to Ensemble ListView, supporting horizontal and vertical scrolling while retaining vertical scrolling as the default.

Related Issue

N/A

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactoring (no functional changes)

What Has Changed

• Added a direction property to ListView, with vertical and horizontal values.
• Passed the configured direction to the underlying scroll view; omitted values default to vertical.
• Added widget tests for the default, horizontal, and explicit vertical directions.
• Updated the Ensemble schema to document the property and its allowed values.

How to Test

Run the focused ListView tests:

cd modules/ensemble
flutter test test/widget/list_view_test.dart

Screenshots / Videos

Not applicable.

Checklist

• I have run flutter analyze and addressed any new warnings
• I have run flutter test and all tests pass
• I have tested my changes on the relevant platform(s)
• I have updated documentation if needed
• My changes do not introduce new warnings or errors