feat(F-059): completed feature

project/frontend/src/app/uploads/[...path]/route.ts

@@ -17,6 +17,14 @@ import path from 'node:path';
 export const dynamic = 'force-dynamic';
 
 const THUMB_SIZES: Readonly<Record<string, number>> = { '40': 40, '200': 200 };
+/**
+ * Maximum height ratio (h/w) for cached thumbnails. The thumbnail is scaled
+ * to fit inside a `width × width * MAX_HEIGHT_RATIO` bounding box without
+ * cropping, so a non-square source produces a non-square thumbnail that
+ * preserves the original aspect ratio. The frontend renders the result with
+ * `object-contain`.
+ */
+const MAX_HEIGHT_RATIO = 1.4;
 const SAFE_SEGMENT = /^[A-Za-z0-9._-]+$/;
 const CONTENT_TYPE_BY_EXTENSION: Readonly<Record<string, string>> = {
   '.jpg': 'image/jpeg',
@@ -55,7 +63,10 @@ async function findOriginal(filename: string): Promise<{ root: string; buffer: B
 async function buildThumbnail(source: Buffer, width: number): Promise<Buffer | null> {
   try {
     const { default: sharp } = await import('sharp');
-    return await sharp(source).resize({ width, withoutEnlargement: true }).toBuffer();
+    const maxHeight = Math.round(width * MAX_HEIGHT_RATIO);
+    return await sharp(source)
+      .resize({ width, height: maxHeight, fit: 'inside', withoutEnlargement: true })
+      .toBuffer();
   } catch {
     return null;
   }