feat: [file] API Resource에서 image_url (presigned URL) 반환

- File 모델에 presignedUrl() 메서드 추가
- GuiderailModelResource: image_url + components[].image_url 반환
- BendingItemResource: image_url 반환
- 소비자(MNG, React)가 별도 처리 없이 R2 직접 로드 가능

app/Http/Resources/Api/V1/BendingItemResource.php

@@ -40,6 +40,7 @@ public function toArray(Request $request): array
             'registration_date' => $this->getOption('registration_date'),
             // 이미지
             'image_file_id' => $this->getImageFileId(),
+            'image_url' => $this->getImageUrl(),
             // 추적
             'legacy_bending_id' => $this->legacy_bending_id,
             'legacy_bending_num' => $this->legacy_bending_id, // MNG2 호환
@@ -60,13 +61,21 @@ public function toArray(Request $request): array
         ];
     }
 
-    private function getImageFileId(): ?int
+    private function getImageFile(): ?\App\Models\Commons\File
     {
-        $file = $this->files()
+        return $this->files()
             ->where('field_key', 'bending_diagram')
             ->orderByDesc('id')
             ->first();
+    }
 
-        return $file?->id;
+    private function getImageFileId(): ?int
+    {
+        return $this->getImageFile()?->id;
+    }
+
+    private function getImageUrl(): ?string
+    {
+        return $this->getImageFile()?->presignedUrl();
     }
 }