fix: add channel to event api subscription key

[olivermrose]

redo of #169

[Copilot]

Pull request overview

This PR fixes the 7TV event subscription system by adding channel identification to subscription keys, preventing conflicts when managing subscriptions for multiple channels. The implementation follows the same pattern already established by the EventSub client.

Key changes:

• Updated all 7TV subscription methods to include a channel parameter
• Changed subscription key format from event to channel:event
• Modified unsubscribe_all to filter subscriptions by channel prefix

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/lib/handlers/seventv/user-update.ts	Updated resub_emote_set invocation to include the channel username parameter
src-tauri/src/seventv/mod.rs	Added channel parameter to resub_emote_set command and updated subscribe/unsubscribe calls
src-tauri/src/seventv/client.rs	Refactored subscription methods to accept channel parameter and use channel:event keys; improved unsubscribe_all to filter by channel prefix
src-tauri/src/api.rs	Updated all 7TV subscription calls in join/leave functions to include channel parameter

After thoroughly reviewing this pull request, I found no issues with the implementation. The changes are consistent, well-structured, and follow existing patterns in the codebase. All subscription-related calls have been properly updated to include the channel parameter, and the new scoping mechanism should prevent subscription conflicts across multiple channels.

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