feat(co-sign): add invite code display in CoSignSession page

- Add invite_code retrieval in GetSignSessionStatus (backend)
- Add inviteCode to cosign:getSessionStatus response (frontend IPC)
- Add inviteCode to SessionState and display UI in CoSignSession

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

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

backend/mpc-system/services/account/adapters/input/http/co_managed_handler.go

@@ -616,6 +616,13 @@ func (h *CoManagedHTTPHandler) GetSignSessionStatus(c *gin.Context) {
 		return
 	}
 
+	// Get invite_code from database
+	var inviteCode string
+	if h.db != nil {
+		row := h.db.QueryRowContext(ctx, `SELECT invite_code FROM mpc_sessions WHERE id = $1`, sessionID)
+		row.Scan(&inviteCode) // Ignore error, invite_code is optional
+	}
+
 	result := gin.H{
 		"session_id":        sessionID,
 		"status":            resp.Status,
@@ -626,6 +633,11 @@ func (h *CoManagedHTTPHandler) GetSignSessionStatus(c *gin.Context) {
 		"total_parties":     resp.TotalParties,
 	}
 
+	// Add invite_code if available
+	if inviteCode != "" {
+		result["invite_code"] = inviteCode
+	}
+
 	// Add signature if sign completed
 	if resp.SessionType == "sign" && len(resp.Signature) > 0 {
 		result["signature"] = hex.EncodeToString(resp.Signature)

backend/mpc-system/services/service-party-app/electron/main.ts

@@ -1839,6 +1839,7 @@ function setupIpcHandlers() {
           sessionId: result?.session_id,
           status: result?.status,
           joinedCount: result?.joined_count,
+          inviteCode: (result as { invite_code?: string })?.invite_code || '',
           threshold: {
             t: result?.threshold_t || activeCoSignSession?.threshold?.t || 0,
             n: result?.threshold_n || activeCoSignSession?.threshold?.n || 0,

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

@@ -26,6 +26,7 @@ interface SessionState {
   sessionId: string;
   walletName: string;
   messageHash: string;
+  inviteCode?: string;
   threshold: { t: number; n: number };
   status: 'waiting' | 'ready' | 'processing' | 'completed' | 'failed';
   participants: Participant[];
@@ -59,6 +60,7 @@ export default function CoSignSession() {
           sessionId: result.session.sessionId || sessionId,
           walletName: result.session.walletName || '',
           messageHash: result.session.messageHash || '',
+          inviteCode: result.session.inviteCode || '',
           threshold: result.session.threshold || { t: 0, n: 0 },
           status: mapStatus(result.session.status),
           participants: (result.session.participants || []).map(p => ({
@@ -341,6 +343,31 @@ export default function CoSignSession() {
         </div>
 
         <div className={styles.content}>
+          {/* 邀请码 - 等待状态时显示 */}
+          {session.inviteCode && session.status === 'waiting' && (
+            <div className={styles.section}>
+              <h3 className={styles.sectionTitle}>邀请码</h3>
+              <div className={styles.publicKeyWrapper}>
+                <code className={styles.publicKey}>{session.inviteCode}</code>
+                <button
+                  className={styles.copyButton}
+                  onClick={async () => {
+                    try {
+                      await navigator.clipboard.writeText(session.inviteCode!);
+                    } catch (err) {
+                      console.error('Failed to copy:', err);
+                    }
+                  }}
+                >
+                  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>
+            </div>
+          )}
+
           {/* 消息哈希 */}
           {session.messageHash && (
             <div className={styles.section}>