fix(app): Segment/@Prop 响应式修复 + 相册选择超时 120s + 换装 500 纯文本 body 友好提示

- Segment.selected 改 @Prop：发型页性别分段高亮不跟手（父层刷新不同步）
- FormRow value/errorText 改 @Prop：诊断表单选择器行文案不回填（真机复测通过）
- SELECT_TIMEOUT_MS 60s→120s：相册选择器冷启动超时后系统浮层成孤儿，点击全失效
- changeCloth 非 JSON body（服务端 500 Internal Server Error）→『服务繁忙，请稍后重试』
- 真机验证：换装请求链路 OK（cloth post 390KB/打点齐全）；服务端 GPU（ComfyUI 正式+备份）当前宕机，生成结果待服务恢复后复验

app/entry/src/main/ets/components/f2/Segment.ets

@@ -10,7 +10,7 @@ import { COLOR_PRIMARY, COLOR_IMAGE_BG, COLOR_TEXT_PRIMARY } from '../../core/Th
 @Component
 export struct Segment {
   items: string[] = []
-  selected: number = 0
+  @Prop selected: number = 0
   onSelect: (idx: number) => void = (_idx: number) => {}
 
   build() {

app/entry/src/main/ets/core/ImageCodec.ets

@@ -41,7 +41,7 @@ const LONG_EDGE: number = 1600
 const JPEG_QUALITY: number = 85
 const IMG_DOMAIN: number = 0x0001
 const IMG_TAG: string = 'MEIDA_IMG'
-const SELECT_TIMEOUT_MS: number = 60000 // 相册选图兜底：系统弹窗最多等 60s
+const SELECT_TIMEOUT_MS: number = 120000 // 相册选图兜底：冷启动+用户浏览常超 60s（超时后系统浮层成孤儿，点击全失效）
 const CAMERA_TIMEOUT_MS: number = 120000 // 拍照兜底：给足取景与确认时间
 
 export class ImageCodec {

app/entry/src/main/ets/core/TryonApi.ets

@@ -181,7 +181,13 @@ export class TryonApi {
       const respText: string = (resp.result ?? '') as string
       hilog.info(TRYON_DOMAIN, TRYON_TAG, 'cloth resp code=%{public}d body=%{public}s',
         resp.responseCode, respText.substring(0, 300))
-      const wire = JSON.parse(respText) as ChangeClothWire
+      let wire: ChangeClothWire
+      try {
+        wire = JSON.parse(respText) as ChangeClothWire
+      } catch (_p) {
+        // 服务端 500 等会回纯文本 body（如 "Internal Server Error"）：按服务繁忙口径提示
+        throw new ApiError(50000, '服务繁忙，请稍后重试', '换装服务暂时不可用')
+      }
       if (wire.ret === 0 && wire.data !== undefined && wire.data.length > 0) {
         return wire.data
       }