✨ Add support for other substitution types

- Store and display original substitution type text
- Treat "eigenverantwortliches Arbeiten" as cancellation

server/prisma/schema.prisma

@@ -27,6 +27,7 @@ model Substitution {
   class          String[]
   date           DateTime
   type           String
+  rawType        String   @default("unknown")
   lesson         Int
   teacher        String
   changedTeacher String?