Feat periodic session checks

[bjoern-m]

Description

This PR includes an overhaul of session management within the SDK.

Implementation

1. Improved Session Validation

• Updated the Scheduler to support periodic and timeout-based session validation.
• Added configurable intervals and callback mechanisms for enhanced session handling.

2. BroadcastChannel Integration

• Introduced the SessionChannel class to facilitate inter-tab communication for session-related events, including expiration, creation, and leadership requests for session validation.

3. Visibility and Activity Tracking

• Developed the WindowActivityManager to monitor window focus, blur, and visibility changes.
• Ensures session validation occurs only in the active tab or window, optimizing performance and resource usage.

4. Session Created Event Changes

• The optional jwt field is no longer included in the session-created-event.
• The expirationSeconds field has been deprecated.
• Instead, the token claims are now passed through the session-created-event and shared across all browser windows or tabs.

5. Deprecation of the is_valid() Function

• The hanko.session.is_valid() function is now deprecated.
• It now functions similarly to await hanko.sessionClient.validate() by requesting the API to check the session but blocks the browser threads.
• Users are advised to use the non-blocking hanko.sessionClient.validate() instead.

6. Local Storage Clean-Up

• Removed the need to store session-related information, such as the JWT or its expiry, in local storage.
• All session-related data is now managed without relying on local storage.