feat: [esign] OTP 인증코드 SMS 발송 기능 추가

- send_method가 alimtalk/both일 때 SMS로 OTP 발송
- 바로빌 sendATKakaotalkEx SMS 대체발송 기능 활용
- SMS 실패 시 이메일 폴백
- auth.blade.php UI 메시지 SMS/이메일 분기 표시

app/Http/Controllers/ESign/EsignPublicController.php

@@ -127,11 +127,13 @@ public function getContract(string $token): JsonResponse
                     'id' => $signer->id,
                     'name' => $signer->name,
                     'email' => $signer->email,
+                    'phone' => $signer->phone,
                     'role' => $signer->role,
                     'status' => $signer->status,
                     'has_stamp' => (bool) $signer->signature_image_path,
                     'signed_at' => $signer->signed_at,
                 ],
+                'send_method' => $contract->send_method ?? 'email',
                 'is_signable' => $isSignable,
                 'status_message' => $statusMessage,
             ],
@@ -161,10 +163,28 @@ public function sendOtp(string $token): JsonResponse
             'otp_attempts' => 0,
         ]);
 
-        // OTP 이메일 발송
-        \Illuminate\Support\Facades\Mail::to($signer->email)->send(
-            new \App\Mail\EsignOtpMail($signer->name, $otpCode)
-        );
+        $sendMethod = $contract->send_method ?? 'email';
+        $channel = 'email';
+
+        // 알림톡/both 방식이고 전화번호가 있으면 SMS로 발송
+        if (in_array($sendMethod, ['alimtalk', 'both']) && $signer->phone) {
+            $smsSent = $this->sendOtpViaSms($contract, $signer, $otpCode);
+            if ($smsSent) {
+                $channel = 'sms';
+            } else {
+                // SMS 실패 시 이메일 폴백
+                if ($signer->email) {
+                    Mail::to($signer->email)->send(new \App\Mail\EsignOtpMail($signer->name, $otpCode));
+                    $channel = 'email';
+                } else {
+                    return response()->json(['success' => false, 'message' => 'OTP 발송에 실패했습니다.'], 500);
+                }
+            }
+        } else {
+            // 이메일 방식 또는 전화번호 없음
+            Mail::to($signer->email)->send(new \App\Mail\EsignOtpMail($signer->name, $otpCode));
+            $channel = 'email';
+        }
 
         EsignAuditLog::create([
             'tenant_id' => $contract->tenant_id,
@@ -173,11 +193,19 @@ public function sendOtp(string $token): JsonResponse
             'action' => 'otp_sent',
             'ip_address' => request()->ip(),
             'user_agent' => request()->userAgent(),
-            'metadata' => ['email' => $signer->email],
+            'metadata' => [
+                'channel' => $channel,
+                'email' => $channel === 'email' ? $signer->email : null,
+                'phone' => $channel === 'sms' ? $signer->phone : null,
+            ],
             'created_at' => now(),
         ]);
 
-        return response()->json(['success' => true, 'message' => '인증 코드가 발송되었습니다.']);
+        return response()->json([
+            'success' => true,
+            'message' => '인증 코드가 발송되었습니다.',
+            'channel' => $channel,
+        ]);
     }
 
     /**
@@ -585,6 +613,74 @@ public function downloadDocument(string $token): StreamedResponse|JsonResponse
 
     // ─── Private ───
 
+    /**
+     * SMS로 OTP 발송 (바로빌 알림톡 SMS 대체발송 기능 활용)
+     */
+    private function sendOtpViaSms(EsignContract $contract, EsignSigner $signer, string $otpCode): bool
+    {
+        try {
+            $member = BarobillMember::where('tenant_id', $contract->tenant_id)->first();
+            if (! $member || ! $member->manager_hp) {
+                Log::warning('OTP SMS 발송 실패: 바로빌 회원 또는 발신번호 없음', [
+                    'contract_id' => $contract->id,
+                    'tenant_id' => $contract->tenant_id,
+                ]);
+
+                return false;
+            }
+
+            $barobill = app(BarobillService::class);
+            $barobill->setServerMode($member->server_mode ?? 'production');
+
+            // 채널 ID 조회
+            $channelResult = $barobill->getKakaotalkChannels($member->biz_no);
+            $yellowId = '';
+            if ($channelResult['success'] ?? false) {
+                $chData = $channelResult['data'];
+                if (is_object($chData) && isset($chData->KakaotalkChannel)) {
+                    $ch = is_array($chData->KakaotalkChannel) ? $chData->KakaotalkChannel[0] : $chData->KakaotalkChannel;
+                    $yellowId = $ch->ChannelId ?? '';
+                }
+            }
+
+            $smsText = "[SAM] 전자계약 인증코드: {$otpCode} (5분 이내 입력)";
+
+            $result = $barobill->sendATKakaotalkEx(
+                corpNum: $member->biz_no,
+                senderId: $member->barobill_id,
+                yellowId: $yellowId,
+                templateName: '인증코드',
+                receiverName: $signer->name,
+                receiverNum: preg_replace('/[^0-9]/', '', $signer->phone),
+                title: '',
+                message: $smsText,
+                buttons: [],
+                smsMessage: $smsText,
+                smsSenderNum: preg_replace('/[^0-9]/', '', $member->manager_hp),
+            );
+
+            if ($result['success'] ?? false) {
+                return true;
+            }
+
+            Log::warning('OTP SMS 발송 API 실패', [
+                'contract_id' => $contract->id,
+                'signer_id' => $signer->id,
+                'error' => $result['error'] ?? 'Unknown',
+            ]);
+
+            return false;
+        } catch (\Throwable $e) {
+            Log::error('OTP SMS 발송 예외', [
+                'contract_id' => $contract->id,
+                'signer_id' => $signer->id,
+                'error' => $e->getMessage(),
+            ]);
+
+            return false;
+        }
+    }
+
     private function sendCompletionAlimtalk(EsignContract $contract, EsignSigner $signer): array
     {
         try {