feat: [재무] 어음 V8 + 상품권 접대비 연동 + 일반전표/계정과목 API

- Bill 확장 필드 (V8), Loan 상품권 카테고리/접대비 자동 연동
- GeneralJournalEntry CRUD, AccountSubject API
- 접대비/복리후생비 날짜 필터, 매출채권 soft delete 제외
- 바로빌 연동 API 엔드포인트 추가
- 부가세 상세 조회 API

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Models/Tenants/JournalEntryLine.php

@@ -0,0 +1,45 @@
+<?php
+
+namespace App\Models\Tenants;
+
+use App\Traits\BelongsToTenant;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+class JournalEntryLine extends Model
+{
+    use BelongsToTenant;
+
+    protected $fillable = [
+        'tenant_id',
+        'journal_entry_id',
+        'line_no',
+        'dc_type',
+        'account_code',
+        'account_name',
+        'trading_partner_id',
+        'trading_partner_name',
+        'debit_amount',
+        'credit_amount',
+        'description',
+    ];
+
+    protected $casts = [
+        'line_no' => 'integer',
+        'debit_amount' => 'integer',
+        'credit_amount' => 'integer',
+        'trading_partner_id' => 'integer',
+    ];
+
+    // DC Type
+    public const DC_DEBIT = 'debit';
+    public const DC_CREDIT = 'credit';
+
+    /**
+     * 전표 관계
+     */
+    public function journalEntry(): BelongsTo
+    {
+        return $this->belongsTo(JournalEntry::class);
+    }
+}