feat(frontend): add discord callback page

this only handles existing accounts for now, still need to write an action function

Foxnouns.Frontend/app/lib/api/auth.ts

@@ -6,6 +6,15 @@ export type AuthResponse = {
 	expires_at: string;
 };
 
+export type CallbackResponse = {
+	has_account: boolean;
+	ticket?: string;
+	remote_username?: string;
+	user?: User;
+	token?: string;
+	expires_at?: string;
+};
+
 export type AuthUrls = {
 	discord?: string;
 	google?: string;