feat: 문서 관리 시스템 FormRequest 구현 (Phase 1.7)

- IndexRequest: 목록 조회 필터/페이징 검증
- StoreRequest: 문서 생성 검증 (템플릿, 데이터, 첨부파일)
- UpdateRequest: 문서 수정 검증

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

app/Http/Requests/Document/IndexRequest.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace App\Http\Requests\Document;
+
+use App\Models\Documents\Document;
+use Illuminate\Foundation\Http\FormRequest;
+
+class IndexRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return true;
+    }
+
+    public function rules(): array
+    {
+        $statuses = implode(',', [
+            Document::STATUS_DRAFT,
+            Document::STATUS_PENDING,
+            Document::STATUS_APPROVED,
+            Document::STATUS_REJECTED,
+            Document::STATUS_CANCELLED,
+        ]);
+
+        return [
+            'status' => "nullable|string|in:{$statuses}",
+            'template_id' => 'nullable|integer',
+            'search' => 'nullable|string|max:100',
+            'from_date' => 'nullable|date',
+            'to_date' => 'nullable|date|after_or_equal:from_date',
+            'sort_by' => 'nullable|string|in:created_at,document_no,title,status,submitted_at,completed_at',
+            'sort_dir' => 'nullable|string|in:asc,desc',
+            'per_page' => 'nullable|integer|min:1|max:100',
+            'page' => 'nullable|integer|min:1',
+        ];
+    }
+}