feat(ui): add QR code display for invite code in signing session

Android TransferScreen:
- Add QR code display above invite code text
- Import QRCodeWriter and related components
- Add generateInviteQRCode helper function
- Update hint text to mention scanning

Electron CoSignSession:
- Import QRCodeSVG from qrcode.react
- Add QR code above invite code text with proper styling
- Center QR code and update hint text

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

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

backend/mpc-system/services/service-party-android/app/src/main/java/com/durian/tssparty/presentation/screens/TransferScreen.kt

@@ -23,10 +23,16 @@ import androidx.compose.ui.text.input.KeyboardType
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
+import android.graphics.Bitmap
+import androidx.compose.foundation.Image
+import androidx.compose.foundation.background
+import androidx.compose.ui.graphics.asImageBitmap
 import com.durian.tssparty.domain.model.NetworkType
 import com.durian.tssparty.domain.model.SessionStatus
 import com.durian.tssparty.domain.model.ShareRecord
 import com.durian.tssparty.util.TransactionUtils
+import com.google.zxing.BarcodeFormat
+import com.google.zxing.qrcode.QRCodeWriter
 import com.journeyapps.barcodescanner.ScanContract
 import com.journeyapps.barcodescanner.ScanOptions
 import kotlinx.coroutines.launch
@@ -650,20 +656,48 @@ private fun SigningScreen(
 
         Spacer(modifier = Modifier.height(24.dp))
 
-        // Invite code (if waiting)
+        // Invite code with QR code (if waiting)
         if (sessionStatus == SessionStatus.WAITING && inviteCode != null) {
             Card(
                 colors = CardDefaults.cardColors(
                     containerColor = MaterialTheme.colorScheme.surfaceVariant
                 )
             ) {
-                Column(modifier = Modifier.padding(16.dp)) {
+                Column(
+                    modifier = Modifier.padding(16.dp),
+                    horizontalAlignment = Alignment.CenterHorizontally
+                ) {
                     Text(
                         text = "邀请码",
                         style = MaterialTheme.typography.labelMedium,
-                        color = MaterialTheme.colorScheme.onSurfaceVariant
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                        modifier = Modifier.fillMaxWidth()
                     )
-                    Spacer(modifier = Modifier.height(8.dp))
+
+                    Spacer(modifier = Modifier.height(16.dp))
+
+                    // QR Code for invite code
+                    val qrBitmap = remember(inviteCode) {
+                        generateInviteQRCode(inviteCode, 200)
+                    }
+                    qrBitmap?.let { bitmap ->
+                        Box(
+                            modifier = Modifier
+                                .size(200.dp)
+                                .background(Color.White),
+                            contentAlignment = Alignment.Center
+                        ) {
+                            Image(
+                                bitmap = bitmap.asImageBitmap(),
+                                contentDescription = "邀请码二维码",
+                                modifier = Modifier.size(200.dp)
+                            )
+                        }
+                    }
+
+                    Spacer(modifier = Modifier.height(16.dp))
+
+                    // Invite code text with copy button
                     Row(
                         modifier = Modifier.fillMaxWidth(),
                         horizontalArrangement = Arrangement.SpaceBetween,
@@ -679,11 +713,15 @@ private fun SigningScreen(
                             Text("复制")
                         }
                     }
+
                     Spacer(modifier = Modifier.height(8.dp))
+
                     Text(
-                        text = "将此邀请码分享给其他签名参与者",
+                        text = "扫描二维码或分享邀请码给其他签名参与者",
                         style = MaterialTheme.typography.bodySmall,
-                        color = MaterialTheme.colorScheme.onSurfaceVariant
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                        textAlign = TextAlign.Center,
+                        modifier = Modifier.fillMaxWidth()
                     )
                 }
             }
@@ -1089,3 +1127,24 @@ private fun InfoRow(label: String, value: String) {
         )
     }
 }
+
+/**
+ * Generate QR code bitmap for invite code
+ */
+private fun generateInviteQRCode(content: String, size: Int): Bitmap? {
+    return try {
+        val writer = QRCodeWriter()
+        val bitMatrix = writer.encode(content, BarcodeFormat.QR_CODE, size, size)
+        val width = bitMatrix.width
+        val height = bitMatrix.height
+        val bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565)
+        for (x in 0 until width) {
+            for (y in 0 until height) {
+                bitmap.setPixel(x, y, if (bitMatrix[x, y]) android.graphics.Color.BLACK else android.graphics.Color.WHITE)
+            }
+        }
+        bitmap
+    } catch (e: Exception) {
+        null
+    }
+}

backend/mpc-system/services/service-party-app/src/pages/CoSignSession.tsx

@@ -1,5 +1,6 @@
 import { useState, useEffect, useCallback } from 'react';
 import { useParams, useNavigate } from 'react-router-dom';
+import { QRCodeSVG } from 'qrcode.react';
 import styles from './Session.module.css';
 import {
   finalizeTransaction,
@@ -346,6 +347,28 @@ export default function CoSignSession() {
           {session.inviteCode && session.status === 'waiting' && (
             <div className={styles.section}>
               <h3 className={styles.sectionTitle}>邀请码</h3>
+
+              {/* QR Code */}
+              <div style={{
+                display: 'flex',
+                justifyContent: 'center',
+                marginBottom: 'var(--spacing-md)',
+              }}>
+                <div style={{
+                  padding: 'var(--spacing-md)',
+                  backgroundColor: 'white',
+                  borderRadius: 'var(--radius-md)',
+                  border: '1px solid var(--border-color)',
+                }}>
+                  <QRCodeSVG
+                    value={session.inviteCode}
+                    size={180}
+                    level="M"
+                    includeMargin={false}
+                  />
+                </div>
+              </div>
+
               <div className={styles.publicKeyWrapper}>
                 <code className={styles.publicKey}>{session.inviteCode}</code>
                 <button
@@ -361,8 +384,8 @@ export default function CoSignSession() {
                   复制
                 </button>
               </div>
-              <p style={{ fontSize: '12px', color: 'var(--text-secondary)', marginTop: 'var(--spacing-xs)' }}>
-                将此邀请码分享给其他参与方，他们可以使用此码加入签名
+              <p style={{ fontSize: '12px', color: 'var(--text-secondary)', marginTop: 'var(--spacing-xs)', textAlign: 'center' }}>
+                扫描二维码或分享邀请码给其他参与方加入签名
               </p>
             </div>
           )}