支持按用户保存播放器与弹幕偏好

在 user 记录上新增播放器音量、弹幕开关、透明度、字号、显示区域、合并偏好、自定义弹幕源以及 dandanplay 应用凭据字段，并提供 PUT /danmaku/settings 局部更新接口，带取值校验。
返回脱敏后的完整渲染配置，绝不回传应用密钥，仅在响应中标记密钥是否已配置。
结果缓存键加入用户 ID 与凭据指纹，避免不同用户或凭据串用缓存；旧版实例级设置仅作为未登录与迁移期的回退。

web/src/utils/withoutVideoFrame.ts

@@ -0,0 +1,27 @@
+/**
+ * JASSUB probes color space with `new VideoFrame(video)` during construct.
+ * Direct-play 302s to a CDN / remote Emby taint <video>, and Chrome throws
+ * SecurityError. Overlay rendering uses requestVideoFrameCallback metadata,
+ * not pixels, so hide VideoFrame for the sync constructor call.
+ *
+ * ponytail: skips color-space matching for all ASS playback, not only tainted
+ * sources. 302 completes after construct, so we cannot probe currentSrc first.
+ * Upgrade: canvas-only JASSUB driven by rVFC metadata when the element taints.
+ */
+export function runWithoutGlobalVideoFrame<T>(fn: () => T): T {
+  const desc = Object.getOwnPropertyDescriptor(globalThis, 'VideoFrame')
+  Object.defineProperty(globalThis, 'VideoFrame', {
+    configurable: true,
+    writable: true,
+    value: undefined,
+  })
+  try {
+    return fn()
+  } finally {
+    if (desc) {
+      Object.defineProperty(globalThis, 'VideoFrame', desc)
+    } else {
+      delete (globalThis as { VideoFrame?: unknown }).VideoFrame
+    }
+  }
+}