list all preauth keys without user filter

headscale 0.28 added GET /v1/preauthkey without a user param
which returns all keys including tag-only ones. this change
adds getAllPreAuthKeys() and uses it when available, falling
back to per-user fetching on older versions.

the UI now handles keys where user is null, showing them as
Tag Only in the filter dropdown.

closes #432

Amp-Thread-ID: https://ampcode.com/threads/T-019c9861-2d45-73ef-ab94-5fce62f63670
Co-authored-by: Amp <amp@ampcode.com>

app/server/headscale/api/endpoints/pre-auth-keys.ts

@@ -3,6 +3,11 @@ import type { PreAuthKey } from "~/types";
 import { defineApiEndpoints } from "../factory";
 
 export interface PreAuthKeyEndpoints {
+  /**
+   * List all pre-auth keys. Requires Headscale 0.28+.
+   */
+  getAllPreAuthKeys(): Promise<PreAuthKey[]>;
+
   /**
    * Retrieves all pre-authentication keys for a specific user.
    *
@@ -33,6 +38,14 @@ export interface PreAuthKeyEndpoints {
 }
 
 export default defineApiEndpoints<PreAuthKeyEndpoints>((client, apiKey) => ({
+  getAllPreAuthKeys: async () => {
+    const { preAuthKeys } = await client.apiFetch<{
+      preAuthKeys: PreAuthKey[];
+    }>("GET", "v1/preauthkey", apiKey, {});
+
+    return preAuthKeys;
+  },
+
   getPreAuthKeys: async (user) => {
     const { preAuthKeys } = await client.apiFetch<{
       preAuthKeys: PreAuthKey[];