feat: add reusable ErrorState component with TDD

Add minimal ErrorState component for displaying error messages with optional retry functionality. Supports light/dark themes via TailwindCSS and follows project patterns. All 6 tests passing.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

components/ErrorState.test.tsx

@@ -0,0 +1,44 @@
+import React from 'react'
+import { render, fireEvent } from '@testing-library/react-native'
+import ErrorState from './ErrorState'
+
+describe('ErrorState Component', () => {
+  describe('Basic Rendering', () => {
+    it('should render error message', () => {
+      const { getByText } = render(<ErrorState message="Something went wrong" />)
+      expect(getByText('Something went wrong')).toBeTruthy()
+    })
+
+    it('should render with default message when not provided', () => {
+      const { getByText } = render(<ErrorState />)
+      expect(getByText('An error occurred')).toBeTruthy()
+    })
+  })
+
+  describe('Retry Functionality', () => {
+    it('should render retry button when onRetry is provided', () => {
+      const onRetry = jest.fn()
+      const { getByText } = render(<ErrorState message="Error" onRetry={onRetry} />)
+      expect(getByText('Retry')).toBeTruthy()
+    })
+
+    it('should not render retry button when onRetry is not provided', () => {
+      const { queryByText } = render(<ErrorState message="Error" />)
+      expect(queryByText('Retry')).toBeNull()
+    })
+
+    it('should call onRetry when retry button is pressed', () => {
+      const onRetry = jest.fn()
+      const { getByText } = render(<ErrorState message="Error" onRetry={onRetry} />)
+      fireEvent.press(getByText('Retry'))
+      expect(onRetry).toHaveBeenCalledTimes(1)
+    })
+  })
+
+  describe('Props', () => {
+    it('should accept testID prop', () => {
+      const { getByTestId } = render(<ErrorState testID="error-test" />)
+      expect(getByTestId('error-test')).toBeTruthy()
+    })
+  })
+})