Add shared file storage with folder tree, permissions, and file manager UI

New document hub for centralized file storage — replaces scattered
drives and USB sticks for non-technical SMBs. Three new tables:
storage_folder (nested hierarchy), storage_folder_permission (role
and user-level access control), storage_file.

Backend: folder CRUD with nested paths, file upload/download via
signed URLs, permission checks (view/edit/admin with inheritance
from parent folders), public/private toggle, breadcrumb navigation,
file search.

Frontend: two-panel file manager — collapsible folder tree on left,
icon grid view on right. Folder icons by type, file size display,
upload button, context menu for download/delete. Breadcrumb nav.
Files sidebar link added.

packages/admin/src/routes/_authenticated.tsx

@@ -5,7 +5,7 @@ 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 } from 'lucide-react'
+import { Users, UserRound, HelpCircle, Shield, UserCog, LogOut, User, Wrench, Package, ClipboardList, FolderOpen } from 'lucide-react'
 
 export const Route = createFileRoute('/_authenticated')({
   beforeLoad: () => {
@@ -87,6 +87,7 @@ function AuthenticatedLayout() {
                 )}
               </>
             )}
+            <NavLink to="/files" icon={<FolderOpen className="h-4 w-4" />} label="Files" />
             {canViewUsers && (
               <div className="mt-4 mb-1 px-3">
                 <span className="text-xs font-semibold text-sidebar-foreground/50 uppercase tracking-wide">Admin</span>