Add curator authentication with audit logging and fix empty 3D gallery sessions.

Introduce session-based curator login, gate debug/checkup routes, log mutations to curator_audit_log, and keep guest hall preload public. Fix gallery view mounting so WebGL halls render reliably after navigation.

client/src/pages/HomePage.css

@@ -27,10 +27,20 @@
 .gallery-session-suspended {
   position: fixed;
   inset: 0;
-  z-index: 0;
+  z-index: -1;
   visibility: hidden;
   pointer-events: none;
-  display: none;
+  opacity: 0;
+  overflow: hidden;
+}
+
+.gallery-session-active {
+  position: fixed;
+  inset: 0;
+  z-index: 50;
+  visibility: visible;
+  pointer-events: auto;
+  opacity: 1;
 }
 
 .home-overlay {
@@ -56,7 +66,9 @@
 }
 
 .debug-mode-toggle,
-.checkup-link-btn {
+.checkup-link-btn,
+.curator-login-btn,
+.curator-logout-btn {
   padding: 6px 12px;
   border-radius: 6px;
   border: 1px solid rgba(201, 169, 110, 0.35);
@@ -69,7 +81,9 @@
 }
 
 .debug-mode-toggle:hover,
-.checkup-link-btn:hover {
+.checkup-link-btn:hover,
+.curator-login-btn:hover,
+.curator-logout-btn:hover {
   border-color: #c9a96e;
   color: #e8d5b5;
 }
@@ -116,6 +130,25 @@
   opacity: 0.55;
 }
 
+.curator-session-label {
+  font-size: 11px;
+  color: rgba(201, 169, 110, 0.65);
+  font-family: ui-monospace, 'Cascadia Code', monospace;
+  max-width: 120px;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.curator-login-btn {
+  border-color: rgba(255, 220, 160, 0.35);
+}
+
+.curator-logout-btn {
+  border-color: rgba(201, 169, 110, 0.25);
+  color: rgba(201, 169, 110, 0.6);
+}
+
 .checkup-link-btn {
   text-decoration: none;
 }