频道切换速度优化

[lbb00]

Accelerate channel switching by removing artificial UI delays, reusing player instances, and optimizing the local proxy for streaming.

This PR addresses three key bottlenecks identified in the channel switching flow:

1. UI Delay: Removed a fixed 220ms delay and double-click logic in channel selection, allowing instant playback on single click.
2. Player Initialization: Refactored the video player to reuse instances when switching channels with the same protocol, avoiding costly full destruction and recreation.
3. Network Proxy: Modified the Tauri proxy to use a single reqwest::Client for connection pooling and stream non-m3u8 responses, reducing first-byte latency for media segments.

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[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
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