feat: template and session page for host

[JacobLinCool]

I don't know... Maybe we have a better landing page now?

This pull request includes multiple significant changes aimed at improving the notification system, enhancing session management, and updating schema definitions. The most important changes are grouped by theme as follows:

Notification System Enhancements:

• Added a new notification system with different types (success, error, info, warning) and corresponding icons and colors in Notifications.svelte.
• Introduced a notifications store to manage notifications, including methods to send and dismiss notifications.
• Integrated the notification system into various components, such as QrScanner.svelte, HostView.svelte, and ParticipantView.svelte, to display relevant messages to users. [1] [2] [3]

Session Management Improvements:

• Enhanced the HostView.svelte component to manage session stages (e.g., starting and ending individual and group stages) with corresponding buttons and actions.
• Improved the ParticipantView.svelte component to allow participants to create or join groups and display group information.

Schema Updates:

• Updated various schema files (code.ts, profile.ts, resource.ts, session.ts, template.ts) to use a custom Timestamp type from utils.ts instead of firebase-admin/firestore. [1] [2] [3] [4] [5]
• Added a custom Timestamp type definition in utils.ts to handle Firestore timestamps consistently across server and client environments.

API Authorization:

• Added an authorization check in hooks.server.ts to return a 401 Unauthorized response for API requests if the user is not authenticated.

Layout and UI Enhancements:

• Included the Notifications.svelte component in the main layout (+layout.svelte) to display notifications globally.