feat(viewer,ui04): E02 static fidelity — real photo fixtures, measured shell/photo/collapse specs, edge fade

- fixtures: 8 picsum-seeded real photos (mixed ratios); seedPhoto thumbBytes/browseBytes injection
- e2e E02 block: wrapper shell (195x280/radius/border/#10161E), photo strip (193w, ratio-height, 3px gap), collapse (44/44 hit, 24 visual, sole button), desktop+mobile screenshots
- EmbedStream: top/bottom 12px dark fade (0.12, §2.3 optional item)
- fix(admin): pre-existing eslint globals gap for ElNotification (template drift, blocks lint gate)

Co-Authored-By: Claude Code <noreply@anthropic.com>

apps/viewer/src/pages/embed/EmbedStream.vue

@@ -95,6 +95,26 @@ function onPhotoClick(photo: PublicEmbedPhoto): void {
   overflow: hidden;
   background: #10161e;
 }
+/* 上下 12px 弱暗渐隐（§2.3 可选项，opacity ≤0.12）：暗示滚动照片带被窗口
+ * 裁切（设计稿 soft fade），不遮照片内容、不拦截点击（pointer-events 无）。 */
+.stream-viewport::before,
+.stream-viewport::after {
+  content: '';
+  position: absolute;
+  left: 0;
+  right: 0;
+  height: 12px;
+  z-index: 2;
+  pointer-events: none;
+}
+.stream-viewport::before {
+  top: 0;
+  background: linear-gradient(to bottom, rgba(16, 22, 30, 0.12), rgba(16, 22, 30, 0));
+}
+.stream-viewport::after {
+  bottom: 0;
+  background: linear-gradient(to top, rgba(16, 22, 30, 0.12), rgba(16, 22, 30, 0));
+}
 .stream-track {
   display: flex;
   flex-direction: column;