Markers list, session countdown and licence checks

⭐️ New

• 🔔 Licence checks and expiry notifications.
• ⚠️ Session warning when you start a new session while another is active.
• ⏳ Session countdown with Custom Delay. Launching a session with a custom delay now shows a countdown.
• 📋 Markers list. Jump to different timestamps in your video with the remote.
• ⏱️ Temporary delay adjustment from within the session view.

🔨 Improved

• Significant code refactoring for performance and stability.
• Sessions jump automatically to the Custom Delay as soon as they load.
• Global delay timing options in Settings are greyed out until Custom Delay is on.
• The back arrow on the remote in the Sessions List now closes the app instead of logging you out.
• The server list now appears if you were logged in to a server that can no longer be found.
• The app remembers your last delay setting.
• Clearer countdown text.