Added czech translations. UI tweak on booking form.

src/backend/data.rs

@@ -303,6 +303,17 @@ pub enum SlotType {
     Day
 }
 
+impl Display for SlotType {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", match self {
+            SlotType::Quarter => {"Quarter an hour"}
+            SlotType::Half => {"Half an hour"}
+            SlotType::Hour => {"Hour"}
+            SlotType::Day => {"Day"}
+        })
+    }
+}
+
 fn def_true() -> bool {
     true
 }