[2.3] Story: Implement Autocomplete Component

[adriancofie]

Description

Create a combobox/autocomplete component for search inputs with async data loading, keyboard navigation, and accessibility compliance.

Parent Issue: #EPIC_2

Sub-Tasks

• Determine if this change will impact existing documentation
• Create Autocomplete component structure
• Implement async data source via loadOptions prop
• Implement synchronous options via options prop
• Add debounced input (configurable delay)
• Implement custom option rendering via renderOption
• Add keyboard navigation (up/down, enter, escape)
• Implement clear button
• Add loading state indicator
• Add no results message (customizable)
• Implement ARIA combobox pattern
• Create CSS Module styling
• Export TypeScript interface with generics
• Implement unit tests (90%+ coverage)
• Add jest-axe accessibility test
• Create Storybook documentation

Notes

• Reference existing implementations in clinical-trials-search-app
• ARIA combobox pattern: https://www.w3.org/WAI/ARIA/apg/patterns/combobox/