kompomaatti improvements

[katajakasa]

• Show a nice message for users if the compo is closed and you can no longer add an entry. "Your time is ..."
• Schedule list could be made to show old events
• pnpm + security options
• There is now a language field in the user profile information -- use it for language selection.
• When logging in via the kompomaatti login system, use ?next= argument to make sure the login redirects the user back to the kompomaatti page.
• After compo is sent and compo is locked, it would be nice to be able to still view the sent entry.
• Complaints that allowed (audio) formats are not clear, and mp3/ogg are only ones mentioned (?)