feat: hide authorizer for rental orders, auto-set sale type

Rental orders no longer show the "Authorizer Required?" question or
the Authorizer field. The sale type is automatically set to 'Rentals'
when creating or confirming a rental order. Validation logic also
skips authorizer checks for rental sale type.

Made-with: Cursor

fusion_whitelabels/static/src/css/whitelabel.css

@@ -0,0 +1,3 @@
+.o-mail-Thread-jumpPresent {
+    display: none !important;
+}