## Context
As per PR title: recently updated list just comprises of notebooks and
chats
Note: known API issue that save a notebook doesn't update its
`updated_at` value, so you'll notice that if you save a notebook it
doesn't move up the recently updated list
<img width="281" height="270" alt="image"
src="https://github.com/user-attachments/assets/f637a593-09a7-4df4-85b7-43637f04738d"
/>
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
* **New Features**
* Added a home view displaying recently updated notebooks and chats.
* Recent items are sorted by update time and limited to five entries.
* Added relative timestamps in minutes, hours, or days.
* Chat entries open directly, while notebook entries link to their
explorer view.
* Added an empty state when no recent items are available.
* **Bug Fixes**
* Excluded unsupported chat types from recent-item results.
* Improved handling of unavailable timestamps.
* **Tests**
* Added coverage for sorting, filtering, limits, and relative-time
formatting.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
