Moves the event timeline to the personal dashboard from the header when
the `frontendHeaderRedesign` flag is active.
When the flag is active, it also:
- hides the event timeline and corresponding button in the header
- renders the environment selector next to the time selector instead of
at the other end of the header

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Co-authored-by: Nuno Góis <github@nunogois.com>
Fixes browser console warnings and errors related to the event timeline
and strategy form.
- **Event Timeline**: Addressed a warning where the environment filter
rendered with a default environment value (production) before
environments were fully loaded.
- **Strategy Form**: Resolved an error caused by forwarding the enabled
prop as a boolean.
https://linear.app/unleash/issue/2-2723/add-signals-tip
Adds a tip to the event timeline regarding the usage of signals.
The conditions for it to show up are the following:
- `!signalsSuggestionSeen` - The current user has not closed the tip yet
- `isEnterprise()` - The Unleash instance is an Enterprise instance
(signals are currently Enterprise-only)
- `isAdmin` - The current user is an admin (signals are currently
admin-only)
- `signalsEnabled` - The signals feature flag is currently enabled
- `!loading` - Signal endpoints have not finished loading (prevents
flickering)
- `signalEndpoints.length === 0` - The Unleash instance currently has
zero configured signal endpoints (signals feature is not being used)

https://linear.app/unleash/issue/2-2703/align-with-ux
Timeline UI/UX improvements after sync with UX, including:
- Added some spacing between each event in the grouping tooltip
- Aligned the x events occurred header with filter dropdown
- Improved the strategy icon somewhat so it doesn't look as off center
- New timeline icon
- Improve icon position relative to timestamp on each event in the
grouping tooltip
- Changed text color in dropdowns to a lighter gray
- Removed bold formatting in tooltip
- Adjusted paddings and margins
- Added close button
- Added shadow
- Added left border
There are a few details missing, which will be tackled in separate PRs.

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Co-authored-by: Nuno Góis <github@nunogois.com>
https://linear.app/unleash/issue/2-2700/persist-timeline-state-in-local-storage
Implements persistent state management for the event timeline using
local storage.
I believe this improves UX by persisting both the timeline toggle
(visibility) state and applied filters across page refreshes.
Includes some scouting/refactoring and some workarounds to prevent the
timeline from animating on page load (in most cases).