Direct links to API Center documentation fail with AADSTS50011 redirect URI mismatch

# Description

Navigating directly to a specific API's documentation URL fails to load the resource and breaks the Entra ID authentication flow. Users cannot deep-link or share direct API documentation pages with team members.

# Reproduction steps

Steps to reproduce the behavior:

1. Copy a direct link to an API definition: https://.portal..azure-apicenter.ms/apis/
2. Open the link in an unauthenticated or fresh browser session (or a new tab/window).
3. Observe the page error: "The specified API does not exist."
4. Click Sign in.
5. Observe the Entra ID sign-in failure error: AADSTS50011.# Expected behavior

# Actual behavior

- The page displays "The specified API does not exist." when accessed directly.

- Attempting to authenticate from the deep link fails with:

- AADSTS50011: The redirect URI 'https://.portal..azure-apicenter.ms/apis/' specified in the request does not match the redirect URIs configured for the application ''.

Auth state appears isolated to single-tab memory/session storage rather than persisting across tabs via cookies, breaking multi-tab workflows.

# Expected behavior

- Direct links should resolve correctly.

- If unauthenticated, the portal should initiate the OAuth/Entra ID flow using the standard root redirect URI (e.g., https://.portal..azure-apicenter.ms/ or an auth callback route) and preserve the intended target path via an encoded state parameter or post-login redirect, rather than sending the full API path as the redirect_uri.

# Current Workaround

1. Navigate directly to the portal root: https://.portal..azure-apicenter.ms/
2. Sign in from the homepage.
3. Manually search for the target API.