feat(member): 회원 썸네일 중앙 1대1 크롭 강제

아바타 업로드 시 원본 비율과 무관하게 중앙 기준 정사각형으로 크롭해 헤더와 설정 화면에서 일관된 1:1 썸네일이 노출되도록 맞춘다.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/api/auth/avatar.post.js

@@ -69,6 +69,7 @@ export default defineEventHandler(async (event) => {
   const avatarMinHeight = clampNumber(Number(config.avatarMinHeight || 96), 1, 4096)
   const avatarMaxWidth = clampNumber(Number(config.avatarMaxWidth || 512), avatarMinWidth, 4096)
   const avatarMaxHeight = clampNumber(Number(config.avatarMaxHeight || 512), avatarMinHeight, 4096)
+  const avatarSquareSize = Math.min(avatarMaxWidth, avatarMaxHeight)
   const avatarWebpQuality = clampNumber(Number(config.avatarWebpQuality || 82), 1, 100)
   const formData = await readMultipartFormData(event)
   const file = (formData || []).find((part) => part.name === 'file' && part.filename)
@@ -126,10 +127,10 @@ export default defineEventHandler(async (event) => {
   const resizedBuffer = await sharp(file.data)
     .rotate()
     .resize({
-      width: avatarMaxWidth,
-      height: avatarMaxHeight,
-      fit: 'inside',
-      withoutEnlargement: true
+      width: avatarSquareSize,
+      height: avatarSquareSize,
+      fit: 'cover',
+      position: 'centre'
     })
     .webp({
       quality: avatarWebpQuality