📍 feat: Preserve Deep Link Destinations Through the Auth Redirect Flow (#10275)

* added support for url query param persistance

* refactor: authentication redirect handling

- Introduced utility functions for managing login redirects, including `persistRedirectToSession`, `buildLoginRedirectUrl`, and `getPostLoginRedirect`.
- Updated `Login` and `AuthContextProvider` components to utilize these utilities for improved redirect logic.
- Refactored `useAuthRedirect` to streamline navigation to the login page while preserving intended destinations.
- Cleaned up the `StartupLayout` to remove unnecessary redirect handling, ensuring a more straightforward navigation flow.
- Added a new `redirect.ts` file to encapsulate redirect-related logic, enhancing code organization and maintainability.

* fix: enhance safe redirect validation logic

- Updated the `isSafeRedirect` function to improve validation of redirect URLs.
- Ensured that only safe relative paths are accepted, specifically excluding paths that lead to the login page.
- Refactored the logic to streamline the checks for valid redirect targets.

* test: add unit tests for redirect utility functions

- Introduced comprehensive tests for `isSafeRedirect`, `buildLoginRedirectUrl`, `getPostLoginRedirect`, and `persistRedirectToSession` functions.
- Validated various scenarios including safe and unsafe redirects, URL encoding, and session storage behavior.
- Enhanced test coverage to ensure robust handling of redirect logic and prevent potential security issues.

* chore: streamline authentication and redirect handling

- Removed unused `useLocation` import from `AuthContextProvider` and replaced its usage with `window.location` for better clarity.
- Updated `StartupLayout` to check for pending redirects before navigating to the new chat page, ensuring users are directed appropriately based on their session state.
- Enhanced unit tests for `useAuthRedirect` to verify correct handling of redirect parameters, including encoding of the current path and query parameters.

* test: add unit tests for StartupLayout redirect behavior

- Introduced a new test suite for the StartupLayout component to validate redirect logic based on authentication status and session storage.
- Implemented tests to ensure correct navigation to the new conversation page when authenticated without pending redirects, and to prevent navigation when a redirect URL parameter or session storage redirect is present.
- Enhanced coverage for scenarios where users are not authenticated, ensuring robust handling of redirect conditions.

---------

Co-authored-by: Vamsi Konakanchi <vamsi.k@trackmind.com>
Co-authored-by: Danny Avila <danny@librechat.ai>

client/src/routes/useAuthRedirect.ts

@@ -1,22 +1,33 @@
 import { useEffect } from 'react';
-import { useNavigate } from 'react-router-dom';
+import { useLocation, useNavigate } from 'react-router-dom';
+import { buildLoginRedirectUrl } from '~/utils';
 import { useAuthContext } from '~/hooks';
 
 export default function useAuthRedirect() {
   const { user, roles, isAuthenticated } = useAuthContext();
   const navigate = useNavigate();
+  const location = useLocation();
 
   useEffect(() => {
     const timeout = setTimeout(() => {
-      if (!isAuthenticated) {
-        navigate('/login', { replace: true });
+      if (isAuthenticated) {
+        return;
       }
+
+      if (location.pathname.startsWith('/login')) {
+        navigate('/login', { replace: true });
+        return;
+      }
+
+      navigate(buildLoginRedirectUrl(location.pathname, location.search, location.hash), {
+        replace: true,
+      });
     }, 300);
 
     return () => {
       clearTimeout(timeout);
     };
-  }, [isAuthenticated, navigate]);
+  }, [isAuthenticated, navigate, location]);
 
   return {
     user,