Refactor parts of codebase to TypeScript

src/components/Message.svelte

src/components/MessageComponent.svelte

src/lib/customcodes.ts

src/lib/flags.ts

src/lib/inputhandler.ts

src/lib/messages.ts

src/lib/server/authentication.ts

src/lib/server/database.ts

src/routes/admin/api/articles.ts

src/routes/admin/api/notificationChannels.ts

src/routes/admin/api/transactions.ts

src/routes/admin/api/users.ts

src/routes/api/transactions.ts