feat: implement nested routes for loaner form

We're using this as our testing ground before attempting to refactor all other pages as well.

src/common/animations.rs

@@ -0,0 +1,14 @@
+use leptos_animate::animations::classes::{In, Out};
+
+pub fn pop_in_out() -> (In, Out) {
+    (
+        In::default()
+            .source("opacity-0 -translate-y-2 scale-90")
+            .active("transition-all duration-150 transform-gpu")
+            .target("opacity-100 translate-y-0 scale-100"),
+        Out::default()
+            .source("opacity-100 translate-y-0 scale-100")
+            .active("transition-all duration-150 transform-gpu")
+            .target("opacity-0 -translate-y-2 scale-90"),
+    )
+}