feat: 급여 관리 API 구현 (Phase 2: 3.2)

- 마이그레이션: payrolls, payroll_settings 테이블 생성
- 모델: Payroll (상태관리 draft→confirmed→paid), PayrollSetting
- 서비스: PayrollService (4대보험 계산, 급여명세서)
- 컨트롤러: PayrollController + FormRequest 5개
- API 엔드포인트 13개:
  - 급여 CRUD + confirm/pay/payslip
  - 일괄 계산/확정 (calculate, bulk-confirm)
  - 설정 관리 (settings/payroll)
- Swagger 문서: PayrollApi.php
- i18n: error.php, message.php, validation.php 키 추가

app/Http/Requests/V1/Payroll/UpdatePayrollSettingRequest.php

@@ -0,0 +1,54 @@
+<?php
+
+namespace App\Http\Requests\V1\Payroll;
+
+use Illuminate\Foundation\Http\FormRequest;
+
+class UpdatePayrollSettingRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return true;
+    }
+
+    public function rules(): array
+    {
+        return [
+            'income_tax_rate' => ['nullable', 'numeric', 'min:0', 'max:100'],
+            'resident_tax_rate' => ['nullable', 'numeric', 'min:0', 'max:100'],
+            'health_insurance_rate' => ['nullable', 'numeric', 'min:0', 'max:100'],
+            'long_term_care_rate' => ['nullable', 'numeric', 'min:0', 'max:100'],
+            'pension_rate' => ['nullable', 'numeric', 'min:0', 'max:100'],
+            'employment_insurance_rate' => ['nullable', 'numeric', 'min:0', 'max:100'],
+            'pension_max_salary' => ['nullable', 'numeric', 'min:0'],
+            'pension_min_salary' => ['nullable', 'numeric', 'min:0'],
+            'pay_day' => ['nullable', 'integer', 'min:1', 'max:31'],
+            'auto_calculate' => ['nullable', 'boolean'],
+            'allowance_types' => ['nullable', 'array'],
+            'allowance_types.*.code' => ['required_with:allowance_types', 'string', 'max:20'],
+            'allowance_types.*.name' => ['required_with:allowance_types', 'string', 'max:50'],
+            'allowance_types.*.is_taxable' => ['nullable', 'boolean'],
+            'deduction_types' => ['nullable', 'array'],
+            'deduction_types.*.code' => ['required_with:deduction_types', 'string', 'max:20'],
+            'deduction_types.*.name' => ['required_with:deduction_types', 'string', 'max:50'],
+        ];
+    }
+
+    public function attributes(): array
+    {
+        return [
+            'income_tax_rate' => __('validation.attributes.income_tax_rate'),
+            'resident_tax_rate' => __('validation.attributes.resident_tax_rate'),
+            'health_insurance_rate' => __('validation.attributes.health_insurance_rate'),
+            'long_term_care_rate' => __('validation.attributes.long_term_care_rate'),
+            'pension_rate' => __('validation.attributes.pension_rate'),
+            'employment_insurance_rate' => __('validation.attributes.employment_insurance_rate'),
+            'pension_max_salary' => __('validation.attributes.pension_max_salary'),
+            'pension_min_salary' => __('validation.attributes.pension_min_salary'),
+            'pay_day' => __('validation.attributes.pay_day'),
+            'auto_calculate' => __('validation.attributes.auto_calculate'),
+            'allowance_types' => __('validation.attributes.allowance_types'),
+            'deduction_types' => __('validation.attributes.deduction_types'),
+        ];
+    }
+}