Queue events broadcasted while we are disconnected

[denmeh]

Closes issue #86 .
It needs task #98 before it is merged.

[Copilot]

Pull Request Overview

Implements queued retry logic for broadcasting Nostr events when initial relay delivery fails.

• Extends Channel trait: broadcast methods now take &Event and return a HashSet of failed relay URLs instead of ().
• Introduces QueuedEvent with asynchronous retry (linear backoff) for failed relays.
• CLI now accepts a provided relay list instead of a hard-coded set.

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 8 comments.

File	Description
src/router/channel.rs	Alters Channel trait API and RelayPool implementation to report failed relays.
src/router/actor.rs	Adds QueuedEvent abstraction and retry task for undelivered events.
cli/src/lib.rs	Switches to using relays parameter instead of hard-coded relay list.

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[Copilot]

Pull Request Overview

Copilot reviewed 3 out of 4 changed files in this pull request and generated 6 comments.

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