feat: Move WebCodecs decoder to Web Worker for better scrcpy video streaming performance

To improve scrcpy streams performance when monitoring up to 6 devices concurrently, WebCodecs decoding tasks have been moved off the main thread to a dedicated Web Worker instance for each device.
The application now allocates an OffscreenCanvas that is passed to each worker alongside the scrcpy packet streams. The background Web Worker runs the actual \`@yume-chan/scrcpy-decoder-webcodecs\` logic, resulting in vastly improved stability and responsiveness on the main thread.
Old active Web Workers are automatically tracked and properly terminated when devices disconnect, streams switch codec, or components unmount.

Co-authored-by: RoiArthurB <16764085+RoiArthurB@users.noreply.github.com>

Author: google-labs-jules[bot]