feat(API): 테넌트 로고 업로드 API 추가

- POST /api/v1/tenants/logo 엔드포인트 추가
- TenantLogoUploadRequest: 이미지 유효성 검사 (jpeg, png, gif, webp, 5MB)
- TenantService.uploadLogo(): 기존 로고 삭제 후 새 로고 저장
- 저장 경로: /storage/tenants/{tenant_id}/logo_{timestamp}.{ext}

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/Http/Requests/Tenant/TenantLogoUploadRequest.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace App\Http\Requests\Tenant;
+
+use Illuminate\Foundation\Http\FormRequest;
+
+class TenantLogoUploadRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return true;
+    }
+
+    public function rules(): array
+    {
+        return [
+            'logo' => 'required|image|mimes:jpeg,png,gif,webp|max:5120', // 5MB
+        ];
+    }
+
+    public function messages(): array
+    {
+        return [
+            'logo.required' => __('validation.required', ['attribute' => '로고 이미지']),
+            'logo.image' => __('validation.image', ['attribute' => '로고']),
+            'logo.mimes' => __('validation.mimes', ['attribute' => '로고', 'values' => 'jpeg, png, gif, webp']),
+            'logo.max' => __('validation.max.file', ['attribute' => '로고', 'max' => '5MB']),
+        ];
+    }
+}