refactor: enhance forward authentication UI and API integration

- Updated the alert block in the HandleForwardAuth component to provide clearer requirements for deploying the authentication proxy.
- Added a DnsHelperModal to assist with DNS configuration in the ForwardAuthServers component.
- Refined API input schemas for forward authentication operations to improve type safety and clarity.
- Removed the obsolete forward-auth SSO design document to streamline documentation.

These changes improve the user experience and maintainability of the forward authentication feature across the application.

packages/server/src/db/schema/forward-auth.ts

@@ -47,6 +47,14 @@ export const forwardAuthSettingsRelations = relations(
 
 const domainRegex = /^(?:[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?\.)+[a-z]{2,}$/;
 
+export const apiForwardAuthServerTarget = z.object({
+	serverId: z.string().nullable(),
+});
+
+export const apiForwardAuthDomainTarget = z.object({
+	domainId: z.string().min(1),
+});
+
 export const apiSetForwardAuthSettings = z.object({
 	serverId: z.string().nullable(),
 	authDomain: z
@@ -60,3 +68,8 @@ export const apiSetForwardAuthSettings = z.object({
 		.default("letsencrypt"),
 	customCertResolver: z.string().optional(),
 });
+
+export const apiDeployForwardAuthOnServer = z.object({
+	serverId: z.string().nullable(),
+	providerId: z.string().min(1),
+});