feat: separate login lobby from workspace

internal/webapp/static/styles.css

@@ -458,6 +458,52 @@ button.is-loading .btn-spinner {
   color: var(--text);
 }
 
+.login-view {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  min-height: 100vh;
+  padding: 28px;
+  background: var(--bg);
+}
+
+.login-card {
+  background: var(--surface);
+  border: 1px solid var(--line);
+  border-radius: 12px;
+  padding: 44px 36px;
+  max-width: 420px;
+  width: 100%;
+  text-align: center;
+}
+
+.login-card h1 {
+  font-size: clamp(32px, 5vw, 52px);
+  margin: 14px 0 18px;
+}
+
+.login-card .lede {
+  margin: 0 auto 28px;
+  max-width: 34ch;
+}
+
+.user-bar {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+  margin-bottom: 18px;
+  padding: 10px 12px;
+  background: var(--surface-muted);
+  border-radius: 6px;
+}
+
+.user-info {
+  font-size: 13px;
+  font-weight: 650;
+  color: var(--text);
+}
+
 @media (max-width: 980px) {
   .workspace {
     grid-template-columns: 1fr;