Add site banner, build number, and changelog

frontend/app/globals.css

@@ -968,6 +968,49 @@ button span {
   border: 1px solid var(--border);
 }
 
+.site-banner {
+  padding: 12px 16px;
+  border-radius: 12px;
+  border: 1px solid var(--border);
+  background: rgba(255, 255, 255, 0.08);
+  color: var(--ink);
+  font-size: 14px;
+}
+
+.site-banner--info {
+  background: rgba(59, 130, 246, 0.18);
+  border-color: rgba(59, 130, 246, 0.4);
+}
+
+.site-banner--warning {
+  background: rgba(255, 200, 87, 0.22);
+  border-color: rgba(255, 200, 87, 0.5);
+}
+
+.site-banner--error {
+  background: rgba(255, 59, 48, 0.2);
+  border-color: rgba(255, 59, 48, 0.4);
+}
+
+.site-banner--maintenance {
+  background: rgba(255, 107, 43, 0.18);
+  border-color: rgba(255, 107, 43, 0.4);
+}
+
+.site-version {
+  position: fixed;
+  left: 16px;
+  bottom: 12px;
+  font-size: 12px;
+  letter-spacing: 0.04em;
+  color: var(--ink-muted);
+  padding: 6px 10px;
+  border-radius: 999px;
+  border: 1px solid var(--border);
+  background: rgba(255, 255, 255, 0.08);
+  z-index: 30;
+}
+
 .recent-header {
   display: flex;
   justify-content: space-between;
@@ -1589,3 +1632,21 @@ button span {
   display: grid;
   gap: 8px;
 }
+
+.changelog-card {
+  gap: 18px;
+}
+
+.changelog-header {
+  display: grid;
+  gap: 8px;
+}
+
+.changelog-list {
+  list-style: disc;
+  padding-left: 22px;
+  display: grid;
+  gap: 10px;
+  color: var(--ink-muted);
+  font-size: 15px;
+}