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/Reservations.razor

@@ -9,7 +9,9 @@
 @rendermode RenderMode.InteractiveServer
 @inject ReservationService ReservationSvc
 
-<h1 class="page-title">External-ID reservations</h1>
+<div class="d-flex justify-content-between align-items-center mb-3">
+    <h4 class="mb-0">External-ID reservations</h4>
+</div>
 <p class="text-muted">
     Fleet-wide ZTag + SAPID reservation state (decision #124). Releasing a reservation is a
     FleetAdmin-only audit-logged action — only release when the physical asset is permanently