fix: refresh Access Settings policy from /access response

Reopening the Access Settings dialog after a save could leave the
radio on the wrong policy: the form initialized `access_policy`
from the route list's snapshot, but the list isn't refreshed when
the dialog closes, so the snapshot's value silently shadowed the
just-saved policy.

Backend now returns the route's authoritative `access_policy` on
`GET /v2/model-routes/{id}/access`. Use that value when the GET
resolves, falling back to the parent snapshot only as the initial
seed so the radio isn't briefly unselected.

While we're here, widen the `access_policy` type from a closed
union to `string` — plugins can contribute additional policy
values via the `accessControl.allowedUsersOverride` slot, so the
wire type shouldn't restrict to the OSS-side enum.

src/pages/llmodels/config/types.ts

@@ -25,7 +25,13 @@ export interface ListItem {
   local_path?: string;
   created_at: string;
   updated_at: string;
-  access_policy: 'public' | 'authed' | 'allowed_users';
+  // Built-in values are 'public' | 'authed' | 'allowed_users';
+  // additional values (e.g. 'allowed_principals') may be contributed
+  // by plugins via `accessControl.prependedPolicies` or by
+  // overriding the default via `accessControl.allowedUsersOverride`.
+  // The `(string & {})` tail keeps literal autocomplete for the
+  // built-ins while still accepting plugin-defined values.
+  access_policy: 'public' | 'authed' | 'allowed_users' | (string & {});
   generic_proxy?: boolean;
   gpu_selector?: {
     gpu_ids: string[];
@@ -346,7 +352,9 @@ export interface BackendOption {
 }
 
 export interface AccessControlFormData {
-  access_policy: 'public' | 'authed' | 'allowed_users';
+  // See `RouteItem.access_policy` for why plugin-defined values are
+  // accepted alongside the built-ins.
+  access_policy: 'public' | 'authed' | 'allowed_users' | (string & {});
   users: { id: number }[];
 }