style(ui): align admin styling with ScadaLink master conventions

- Move CSS into wwwroot/css/ (theme.css, site.css); sidebar 218 -> 220px
- Add hamburger + Bootstrap collapse for <lg viewports
- Add Components/Shared/ with LoadingSpinner, ToastNotification, StatusBadge
- Replace .page-title with flex + <h4 class="mb-0"> across 20 pages
- Convert NewCluster + IdentificationFields forms to card + h6 subsection pattern

src/Server/ZB.MOM.WW.OtOpcUa.Admin/Components/Pages/RoleGrants.razor

@@ -15,9 +15,8 @@
 @inject AdminHubConnectionFactory HubFactory
 @implements IAsyncDisposable
 
-<h1 class="page-title">LDAP group → Admin role grants</h1>
-
-<div class="d-flex justify-content-end mb-3">
+<div class="d-flex justify-content-between align-items-center mb-3">
+    <h4 class="mb-0">LDAP group &rarr; Admin role grants</h4>
     <button class="btn btn-primary btn-sm" @onclick="StartAdd">Add grant</button>
 </div>