feat(image): DownsampledKFImage 추가 및 캐릭터/배너에 공통 적용

- KFImage 공통 옵션(다운샘플링, scaleFactor, backgroundDecode,
  cancelOnDisappear, retry) 캡슐화한 DownsampledKFImage 추가
- 채팅-캐릭터 탭 Character/Recent/배너 뷰에서 인라인 KFImage 제거 → 공통 뷰 적용
- 수평 리스트 HStack → LazyHStack으로 교체해 프리로딩/메모리 개선

Why: 대형 원본 디코딩으로 인한 메모리 스파이크 완화 및 일관된
이미지 로딩 정책 적용. 유지보수성 및 성능 향상.

SodaLive/Sources/Chat/Character/Banner/AutoSlideCharacterBannerView.swift

@@ -84,16 +84,10 @@ private struct AutoSlideCharacterBannerPage: View {
     var body: some View {
         Group {
             if let boundURL {
-                KFImage(boundURL)
+                DownsampledKFImage(
-                    .placeholder { Color.gray.opacity(0.2) }
+                    url: boundURL,
-                    .retry(maxCount: 2, interval: .seconds(1))
+                    size: CGSize(width: width, height: height)
-                    .cancelOnDisappear(true)
+                ).cornerRadius(12)
-                    .downsampling(size: CGSize(width: width, height: height))
-                    .resizable()
-                    .scaledToFill()
-                    .frame(width: width, height: height)
-                    .clipped()
-                    .cornerRadius(12)
             } else {
                 Color.clear
                     .frame(width: width, height: height)

SodaLive/Sources/Chat/Character/CharacterItemView.swift

@@ -22,14 +22,10 @@ struct CharacterItemView: View {
     var body: some View {
         VStack(alignment: .leading, spacing: 4) {
             ZStack(alignment: .bottomLeading) {
-                KFImage(URL(string: character.imageUrl))
+                DownsampledKFImage(
-                    .placeholder { Color.gray.opacity(0.2) }
+                    url: URL(string: character.imageUrl),
-                    .retry(maxCount: 2, interval: .seconds(1))
+                    size: CGSize(width: size, height: size)
-                    .cancelOnDisappear(true)
+                )
-                    .resizable()
-                    .scaledToFill()
-                    .frame(width: size, height: size)
-                    .clipped()
                 .cornerRadius(12)
                 
                 if isShowRank {

SodaLive/Sources/Chat/Character/CharacterSectionView.swift

@@ -32,7 +32,7 @@ struct CharacterSectionView: View {
             .padding(.horizontal, 24)
             
             ScrollView(.horizontal, showsIndicators: false) {
-                HStack(spacing: 16) {
+                LazyHStack(spacing: 16) {
                     ForEach(items.indices, id: \.self) { idx in
                         let item = items[idx]
                         CharacterItemView(

SodaLive/Sources/Chat/Character/Recent/RecentCharacterItemView.swift

@@ -13,13 +13,10 @@ struct RecentCharacterItemView: View {
     
     var body: some View {
         VStack(spacing: 6) {
-            KFImage(URL(string: character.imageUrl))
+            DownsampledKFImage(
-                .placeholder { Circle().fill(Color.gray.opacity(0.2)) }
+                url: URL(string: character.imageUrl),
-                .retry(maxCount: 2, interval: .seconds(1))
+                size: CGSize(width: 76, height: 76)
-                .cancelOnDisappear(true)
+            )
-                .resizable()
-                .scaledToFill()
-                .frame(width: 76, height: 76)
             .clipShape(Circle())
             
             Text(character.name)

SodaLive/Sources/Chat/Character/Recent/RecentCharacterSectionView.swift

@@ -28,7 +28,7 @@ struct RecentCharacterSectionView: View {
             .padding(.horizontal, 24)
             
             ScrollView(.horizontal, showsIndicators: false) {
-                HStack(spacing: 16) {
+                LazyHStack(spacing: 16) {
                     ForEach(items.indices, id: \.self) { idx in
                         let item = items[idx]
                         RecentCharacterItemView(character: item)

SodaLive/Sources/CustomView/DownsampledKFImage.swift

@@ -0,0 +1,45 @@
+//
+//  DownsampledKFImage.swift
+//  SodaLive
+//
+//  Created by klaus on 10/23/25.
+//
+
+import SwiftUI
+import Kingfisher
+
+struct DownsampledKFImage: View {
+    let url: URL?
+    let size: CGSize
+    let cacheOriginal: Bool = false
+    
+    var body: some View {
+        KFImage(url)
+            .placeholder { Color.gray.opacity(0.2) }
+            .retry(maxCount: 2, interval: .seconds(1))
+            .cancelOnDisappear(true)
+            .downsampled(to: size, cacheOriginal: cacheOriginal)
+            .resizable()
+            .scaledToFill()
+            .frame(width: size.width, height: size.height)
+            .clipped()
+    }
+}
+
+extension KFImage {
+    func downsampled(
+        to targetSize: CGSize,
+        scale: CGFloat = UIScreen.main.scale,
+        cacheOriginal: Bool = false
+    ) -> KFImage {
+        let pixel = CGSize(
+            width: targetSize.width * scale,
+            height: targetSize.height * scale
+        )
+        return self
+            .setProcessor(DownsamplingImageProcessor(size: pixel))
+            .scaleFactor(scale)
+            .backgroundDecode()
+            .cacheOriginalImage(cacheOriginal)
+    }
+}