feat: [결재] 양식 마이그레이션 12종 + 반려이력/재상신

- 재직/경력/위촉증명서, 사직서, 사용인감계, 위임장
- 이사회의사록, 견적서, 공문서, 연차사용촉진 1차/2차
- 지출결의서 body_template 고도화
- rejection_history, resubmit_count, drafter_read_at 컬럼
- Document-Approval 브릿지 연동 (linkable)
- 수신함 날짜 범위 필터 추가

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

database/migrations/2026_02_27_200000_add_linkable_to_approvals_table.php

@@ -0,0 +1,32 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * 결재(approvals) 테이블에 연결 대상(linkable) 컬럼 추가
+     * - Document 시스템과 Approval 시스템을 브릿지하기 위한 다형성 관계
+     */
+    public function up(): void
+    {
+        Schema::table('approvals', function (Blueprint $table) {
+            $table->string('linkable_type')->nullable()->after('attachments')->comment('연결 대상 모델 (예: App\\Models\\Documents\\Document)');
+            $table->unsignedBigInteger('linkable_id')->nullable()->after('linkable_type')->comment('연결 대상 ID');
+            $table->index(['linkable_type', 'linkable_id'], 'idx_linkable');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::table('approvals', function (Blueprint $table) {
+            $table->dropIndex('idx_linkable');
+            $table->dropColumn(['linkable_type', 'linkable_id']);
+        });
+    }
+};

database/migrations/2026_03_06_100000_add_resignation_form.php

@@ -0,0 +1,38 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Support\Facades\DB;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        $tenants = DB::table('tenants')->whereNull('deleted_at')->pluck('id');
+
+        foreach ($tenants as $tenantId) {
+            $exists = DB::table('approval_forms')
+                ->where('tenant_id', $tenantId)
+                ->where('code', 'resignation')
+                ->exists();
+
+            if (! $exists) {
+                DB::table('approval_forms')->insert([
+                    'tenant_id' => $tenantId,
+                    'name' => '사직서',
+                    'code' => 'resignation',
+                    'category' => 'certificate',
+                    'template' => '[]',
+                    'body_template' => '',
+                    'is_active' => true,
+                    'created_at' => now(),
+                    'updated_at' => now(),
+                ]);
+            }
+        }
+    }
+
+    public function down(): void
+    {
+        DB::table('approval_forms')->where('code', 'resignation')->delete();
+    }
+};