feat: implement auth callback page

This page will allow users to redirect to their previous path when they sign in.

src/pages/auth_callback.rs

@@ -0,0 +1,37 @@
+use leptos::prelude::*;
+use leptos_oidc::AuthSignal;
+use leptos_router::hooks::use_navigate;
+
+#[component]
+pub fn AuthCallbackPage() -> impl IntoView {
+    // This should wait for authentication, read the values in session storage, and then redirect
+    // to the correct page. The session storage should contain a path, which we'll need to check.
+    
+    let auth = expect_context::<AuthSignal>();
+    let navigate = use_navigate();
+    
+    Effect::new(move || {
+        // Wait for auth to load, then read information.
+        if let Some(_) = auth.get().authenticated() {
+            // Read the sessionStorage to get the last navigated path.
+            let storage_opt = window().session_storage().ok().flatten();
+            let path = storage_opt
+                .and_then(|storage| storage.get_item("post_login_path").ok().flatten())
+                .unwrap_or_else(|| "/".to_string());
+            
+            // Clear storage in case we need to reauth again
+            if let Some(storage) = window().session_storage().ok().flatten() {
+                let _ = storage.remove_item("post_login_path");
+            }
+            
+            // Redirect to the stored path
+            navigate(&path, Default::default());
+        }
+    });
+    
+    view! {
+        <div class="flex flex-col w-full mx-auto items-center justify-center">
+            <p>"Completing the login process..."</p>
+        </div>
+    }
+}