chore(centralui): remove dead .sidebar shell CSS left by the theme cutover

The .sidebar/#sidebar-collapse/.nav-link/.nav-section-toggle block is orphaned —
the side rail is now the ZB.MOM.WW.Theme kit's .side-rail/.rail-link shell, and
no markup references these selectors. Kept the app-only #reconnect-modal and
.script-editor-modal rules (not provided by the kit). 95 lines removed; builds clean.

src/ZB.MOM.WW.ScadaBridge.CentralUI/wwwroot/css/site.css

@@ -1,99 +1,8 @@
 /* ScadaBridge Central UI – global styles. Loaded from Host App.razor as
-   `_content/ZB.MOM.WW.ScadaBridge.CentralUI/css/site.css`. */
+   `_content/ZB.MOM.WW.ScadaBridge.CentralUI/css/site.css`.
-
+   The shared ZB.MOM.WW.Theme kit (linked via <ThemeHead/>) owns the tokens and
-.sidebar {
+   the side-rail shell; this sheet carries only app-specific rules the kit does
-    min-width: 220px;
+   not provide. */
-    max-width: 220px;
-    height: 100vh;
-    background: var(--card);
-    border-right: 1px solid var(--rule-strong);
-}
-
-/* Keep the sidebar pinned to the viewport on lg+ so it stays visible even
-   when the main content scrolls past 100vh. The wrapper is the flex child
-   of MainLayout; align-self prevents the flex row from stretching it. */
-@media (min-width: 992px) {
-    #sidebar-collapse {
-        position: sticky;
-        top: 0;
-        height: 100vh;
-        align-self: flex-start;
-        z-index: 1020;
-    }
-}
-
-.sidebar .nav-link {
-    color: var(--ink-soft);
-    padding: 0.4rem 1rem;
-    font-size: 0.9rem;
-}
-
-.sidebar .nav-link:hover {
-    color: var(--ink);
-    background-color: var(--paper);
-}
-
-.sidebar .nav-link.active {
-    color: var(--accent-deep);
-    background-color: var(--paper);
-    font-weight: 600;
-    /* Left accent so active state isn't carried by color alone. */
-    border-left: 3px solid var(--accent);
-    padding-left: calc(1rem - 3px);
-}
-
-/* Collapsible section header — a full-width button styled as an uppercase
-   eyebrow with a leading expand/collapse chevron. */
-.sidebar .nav-section-toggle {
-    display: flex;
-    align-items: center;
-    gap: 0.4rem;
-    width: 100%;
-    background: none;
-    border: 0;
-    cursor: pointer;
-    text-align: left;
-    color: var(--ink-faint);
-    font-size: 0.7rem;
-    font-weight: 600;
-    text-transform: uppercase;
-    letter-spacing: 0.07em;
-    padding: 0.75rem 1rem 0.25rem;
-    margin-top: 0.5rem;
-}
-
-.sidebar .nav-section-toggle:hover {
-    color: var(--ink);
-}
-
-.sidebar .nav-section-toggle .bi {
-    font-size: 0.8rem;
-    line-height: 1;
-}
-
-.sidebar .brand {
-    color: var(--ink);
-    font-size: 1.1rem;
-    font-weight: 600;
-    letter-spacing: 0.02em;
-    padding: 1rem;
-    border-bottom: 1px solid var(--rule);
-}
-
-/* The single accent glyph in the brand mark. */
-.sidebar .brand .mark {
-    color: var(--accent);
-}
-
-/* When the sidebar is collapsed under <lg viewports the Bootstrap collapse
-   container removes the fixed width; restore full width on mobile. */
-@media (max-width: 991.98px) {
-    .sidebar {
-        min-width: 100%;
-        max-width: 100%;
-        height: auto;
-    }
-}
 
 #reconnect-modal {
     display: none;