[Upgrades] Upgrade the System Version

[AlanaArias1297]

As an administrator, I want to upgrade the system to a new available version, view the installation status history, and be able to cancel or retry in case of interruption.

Steps to reproduce

1. Log in as an administrator.
2. Click on the Upgrade left navigation menu.
3. View the current system version.
4. Select the version to install from the list of available releases.
5. Click the install or stage button.
6. Monitor the upgrade progress.
7. If staging: confirm the installation once complete.
8. If interrupted: click Retry to try again.
9. To cancel: click the Cancel button.

Acceptance Criteria
✓ The user can navigate to the Upgrade page (requires can_upgrade permission).
✓ The current system version is shown: version, build version, deployed by user, and deployment date.
✓ A list of available releases is shown for upgrading.
✓ When an upgrade is in progress, a state history is shown with dates.
✓ If the upgrade is in 'indexing' state, indexing progress is shown with progress bars per database/ddoc.
✓ If the upgrade was staged and is indexed, a button to complete the installation is shown.
✓ If the upgrade was interrupted, a warning and a Retry button are shown.
✓ The Cancel button (danger styling) allows aborting the upgrade at any point.
✓ A success message is shown on completion.
✓ A loading indicator is shown while information is being fetched.
✓ An error alert is shown on failure.