https://linear.app/unleash/issue/2-2665/show-signals-in-the-event-timeline
Implements signals in the event timeline.
This merges events and signals into a unified `TimelineEvent`
abstraction, streamlining the data structure to only include properties
relevant to the timeline.
Key changes:
- Refactors the timeline logic to handle both events and signals through
the new abstraction.
- Introduces the `useSignalQuery` hook, modeled after `useEventSearch`,
as both serve similar purposes, albeit for different resource types.
Note: The signals suggestion alert is not included and will be addressed
in a future task.
