fix(homepage): use app-wide abacus config in interactive flashcards

The interactive flashcards section at the bottom of the homepage was
hardcoding beadShape="circle" instead of respecting the app-wide abacus
configuration context that all other abaci on the site use.

Changes to InteractiveFlashcards.tsx:
- Import useAbacusConfig hook from @soroban/abacus-react
- Call useAbacusConfig() in DraggableCard component
- Use appConfig.beadShape instead of hardcoded "circle"

This ensures visual consistency across all abacus displays on the site
and respects user preferences for bead styling.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

apps/web/src/components/InteractiveFlashcards.tsx

@@ -1,6 +1,6 @@
 'use client'
 
-import { AbacusReact } from '@soroban/abacus-react'
+import { AbacusReact, useAbacusConfig } from '@soroban/abacus-react'
 import { useEffect, useRef, useState } from 'react'
 import { css } from '../../styled-system/css'
 
@@ -93,6 +93,8 @@ interface DraggableCardProps {
 }
 
 function DraggableCard({ card, containerRef }: DraggableCardProps) {
+  const appConfig = useAbacusConfig()
+
   // Track position - starts at initial, updates when dragged
   const [position, setPosition] = useState({ x: card.initialX, y: card.initialY })
   const [rotation, setRotation] = useState(card.initialRotation) // Now dynamic!
@@ -337,7 +339,7 @@ function DraggableCard({ card, containerRef }: DraggableCardProps) {
             transformOrigin: 'center',
           })}
         >
-          <AbacusReact value={card.number} columns={3} beadShape="circle" />
+          <AbacusReact value={card.number} columns={3} beadShape={appConfig.beadShape} />
         </div>
 
         {/* Number display */}