feat: add oidc support with authentik

.env.example

@@ -33,3 +33,11 @@ NEXT_PUBLIC_UMAMI_WEBSITE_ID="your-website-id-here"
 NEXT_PUBLIC_UMAMI_SCRIPT_URL="https://analytics.umami.is/script.js"
 # Build tweaks
 # SKIP_ENV_VALIDATION=1
+
+# SSO / Authentik (Optional - only needed if using SSO authentication)
+# Configure these if you want to enable Single Sign-On with Authentik OIDC
+# The issuer should be your Authentik application's OAuth2 provider URL
+# Example: https://auth.example.com/application/o/your-app-slug
+AUTHENTIK_ISSUER=""
+AUTHENTIK_CLIENT_ID=""
+AUTHENTIK_CLIENT_SECRET=""