[FEAT] Feat update available widget

[SquirrelDeveloper]

This pull request introduces an update notification feature for the application. The main changes include adding a new widget to the client-side, creating a server-side update checker, and integrating it with the existing system.

Client-side changes:

• client/src/app.tsx: Imported and added the UpdateAvailableWidget to the header components. [1] [2]
• client/src/components/HeaderComponents/UpdateAvailableWidget.tsx: Created a new widget to display update notifications using Popover, Badge, and Avatar components.
• client/src/components/Icons/CustomIcons.tsx: Added a new UpdateLine icon for the update widget.

Server-side changes:

• server/src/controllers/rest/user/user.ts: Updated the getCurrentUser function to include the updateAvailable field. [1] [2] [3]
• server/src/core/startup/index.ts: Integrated the UpdateChecker to run during the server startup. [1] [2]
• server/src/data/cache/defaults/index.ts: Added a default value for the UPDATE_AVAILABLE key in the Redis cache.
• server/src/modules/crons/index.ts: Added a cron job to periodically check for updates. [1] [2]
• server/src/modules/update/UpdateChecker.ts: Implemented the UpdateChecker class to fetch the latest version and update the cache.

Shared library changes:

• shared-lib/src/enums/settings.ts: Added UPDATE_AVAILABLE to GeneralSettingsKeys and DefaultValue enums. [1] [2]
• shared-lib/src/types/api.ts: Updated the Settings type to include the updateAvailable field.

Testing:

• server/src/tests/unit-tests/modules/update/UpdateChecker.test.ts: Added unit tests for the UpdateChecker module.