feat(server): add trailing slash normalization and API root endpoint

- Add tower-http normalize-path feature to handle trailing slashes
- Implement NormalizePathLayer to trim trailing slashes from URLs
- Add GET /api/ endpoint with API description message
- Fix OAuth callback redirect to use /api/profile path

pacman-server/src/routes.rs

@@ -175,7 +175,7 @@ pub async fn oauth_callback_handler(
         });
     }
 
-    (StatusCode::FOUND, Redirect::to("/profile")).into_response()
+    (StatusCode::FOUND, Redirect::to("/api/profile")).into_response()
 }
 
 /// Handles the request to the profile endpoint.