feat: add Kontaktformular section with backend logic and styles

Implemented a new Kontaktformular section including a frontend form, backend logic using `mzur/kirby-uniform`, and corresponding styles in `input.css`. Added a new template, controller, and snippet for dynamic rendering and form handling.

src/css/input.css

@@ -70,5 +70,8 @@
         @apply text-sf_blau-500 font-bold hover:text-sf_gelb-600;
     }
 
-
+    .uniform__potty {
+        position: absolute;
+        left: -9999px;
+    }
 }