add providers, LiveDashboard, errors links to admin sidebar

Providers was a hidden page with no nav link. Also adds
LiveDashboard and ErrorTracker to the sidebar footer, and
styles the provider dropdown menu items.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

assets/css/admin/components.css

@@ -472,6 +472,7 @@
     box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
     z-index: 50;
     padding: 0.25rem;
+    list-style: none;
   }
 
   &:focus-within .admin-dropdown-content,
@@ -480,6 +481,27 @@
   }
 }
 
+.admin-dropdown-content li a,
+.admin-dropdown-content li button {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  padding: 0.5rem 0.75rem;
+  border-radius: 0.375rem;
+  font-size: 0.875rem;
+  color: var(--color-base-content);
+  text-decoration: none;
+  cursor: pointer;
+  background: none;
+  border: none;
+  width: 100%;
+  text-align: left;
+
+  &:hover {
+    background-color: var(--color-base-200);
+  }
+}
+
 /* ── Spinner ── */
 
 @keyframes admin-spin {