fix(AutoComplete): improve keyboard navigation and accessibility

[pranjali2076]

What does this PR do?

Improves keyboard accessibility of the AutoComplete component.

Changes

• Backspace removes last selected tag when input is empty
• Enter key now selects correct matching item (fixes stale cursor)
• Partial text match highlights correct option using includes()
• Fixed stale cursor index reset in useCursor hook

Related Issues

Closes #1567

Tests

• Added new test for Backspace key functionality
• All 19 tests passing ✅

WCAG Compliance

Improves WCAG 2.1 SC 2.1.1 keyboard accessibility

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Latest commit: 2f2cc8f

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