Add vault secret manager frontend UI

Three-state page: not initialized → locked → unlocked.
Any user with vault.view can unlock (for store opening).
Admins can lock and change master password.

- Two-panel layout: categories on left, entries on right
- Entry reveal button shows decrypted value for 30s with copy
- Add/edit/delete entries and categories
- KeyRound icon in sidebar navigation

packages/admin/src/routes/_authenticated.tsx

@@ -7,7 +7,7 @@ import { useAuthStore } from '@/stores/auth.store'
 import { myPermissionsOptions } from '@/api/rbac'
 import { Avatar } from '@/components/shared/avatar-upload'
 import { Button } from '@/components/ui/button'
-import { Users, UserRound, HelpCircle, Shield, UserCog, LogOut, User, Wrench, Package, ClipboardList, FolderOpen, Settings } from 'lucide-react'
+import { Users, UserRound, HelpCircle, Shield, UserCog, LogOut, User, Wrench, Package, ClipboardList, FolderOpen, KeyRound, Settings } from 'lucide-react'
 
 export const Route = createFileRoute('/_authenticated')({
   beforeLoad: () => {
@@ -134,6 +134,7 @@ function AuthenticatedLayout() {
               </>
             )}
             <NavLink to="/files" icon={<FolderOpen className="h-4 w-4" />} label="Files" />
+            <NavLink to="/vault" icon={<KeyRound className="h-4 w-4" />} label="Vault" />
             {canViewUsers && (
               <div className="mt-4 mb-1 px-3">
                 <span className="text-xs font-semibold text-sidebar-foreground/50 uppercase tracking-wide">Admin</span>