feat: harden support, localize knowledge and add operator availability [skip ci]

Source-only publication of reviewed commit 64e96a7f423673dc29ad56485be9fc79bce8af1c.

Passed in isolation: focused frontend/backend tests, race checks, TypeScript typecheck, lint, Go compilation, Flowgram build, and deterministic SDK build/tests.

Not accepted as a production release: Next.js export/native assembly remains blocked by environment memory limits; browser interaction and MySQL staging acceptance remain unverified. No production server, database/schema, runtime configuration, deployment, release tag, or workflow execution was performed.

Expected source tree: 0a4a7528e9.

web/lib/navigation.tsx

@@ -38,6 +38,7 @@ export type DashboardNavItemConfig = Omit<DashboardNavMenuItem, "title"> & {
    * admin can see the module.
    */
   requiredPermission?: string;
+  requiredAnyPermission?: readonly string[];
 };
 
 export type DashboardNavSectionConfig = {
@@ -51,6 +52,9 @@ function navItemVisible(
   superAdmin: boolean,
   permissionSet: Set<string>,
 ): boolean {
+  if (item.requiredAnyPermission) {
+    return item.requiredAnyPermission.some((permission) => permissionSet.has(permission));
+  }
   if (superAdmin) {
     return true;
   }
@@ -264,6 +268,12 @@ export const dashboardNavSections: DashboardNavSectionConfig[] = [
     titleKey: "nav.system",
     icon: <ShieldCheckIcon />,
     items: [
+      {
+        titleKey: "supportAvailability.title",
+        url: "/dashboard/support-availability",
+        icon: <CalendarClockIcon />,
+        requiredAnyPermission: ["supportConfig.view", "agentTeamSchedule.view"],
+      },
       {
         titleKey: "nav.setupWizard",
         url: "/dashboard/setup",