Add recording status notification

[roznawsk]

Adds RecordingStatusChanged to ServerMessage so Fishjam can push recording lifecycle transitions (finished/available/failed) with the recording's metadata to the dashboard webhook, per ADR-0048.

No ACTIVE value — recordings are born active (that's the create response, not a transition).

Part of FCE-3518.

[linear]

FCE-3518

[Copilot]

Pull request overview

Adds a new server notification message to expose recording lifecycle transitions to webhook consumers (dashboard), aligning the protobuf schema, generated Elixir bindings, and rendered docs.

Changes:

• Introduces ServerMessage.RecordingStatusChanged with Status enum (FINISHED/AVAILABLE/FAILED) plus recording_id and metadata.
• Adds recording_status_changed as a new ServerMessage oneof content variant (tag 34).
• Regenerates/updates Elixir protobuf modules and the markdown docs to include the new message and enum.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
fishjam/server_notifications.proto	Adds RecordingStatusChanged message + ServerMessage oneof variant for recording status transitions.
fishjam_protos/lib/fishjam/server_notifications.pb.ex	Updates generated Elixir protobuf definitions to include the new enum/message and field.
doc/docs.md	Updates generated documentation/TOC to document the new notification and enum.

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