Notifications page & dropdown improvements

[MartinKolarik]

• new page listing notifications, like https://github.com/notifications (design in Figma)
• restrict the current dropdown to 5 notifications; add a link as the sixth item that leads to the page (see updated Figma)
• animate current dropdown expand/collapse
• improve read/unread indication in the dropdown (see updated Figma)

[MartinKolarik]

@xbpcb for the newly added timestamps, please use this format (add to utils):

export const formatDateTime = (dateTime: string | Date | null) => {
	if (!dateTime) {
		return '';
	}

	if (typeof dateTime === 'string') {
		dateTime = new Date(dateTime);
	}

	return dateTime.toLocaleDateString('en-US', { day: 'numeric', month: 'short', year: 'numeric', hour: 'numeric', minute: 'numeric' });
};