feat: add frontend API helper with env-aware base URL

frontend/src/lib/api.ts

@@ -0,0 +1,45 @@
+export interface TransformOptions {
+  width?: number;
+  height?: number;
+  quality?: number;
+  format?: "png" | "webp" | "jpeg";
+  fit?: "inside" | "outside" | "cover" | "contain";
+  position?:
+    | "center"
+    | "top"
+    | "right"
+    | "bottom"
+    | "left"
+    | "top-left"
+    | "top-right"
+    | "bottom-left"
+    | "bottom-right";
+}
+
+const API_BASE =
+  import.meta.env.DEV ? "http://localhost:3000/api" : "/api";
+
+export async function transformImage(
+  file: File,
+  options: TransformOptions
+): Promise<Blob> {
+  const formData = new FormData();
+  formData.append("file", file);
+
+  Object.entries(options).forEach(([key, value]) => {
+    if (value !== undefined && value !== null) {
+      formData.append(key, String(value));
+    }
+  });
+
+  const res = await fetch(`${API_BASE}/transform`, {
+    method: "POST",
+    body: formData
+  });
+
+  if (!res.ok) {
+    throw new Error("Transform failed");
+  }
+
+  return await res.blob();
+}