refactor: move inline styles to CSS modules

Extract inline fontSize/color styles from LogTab, LayoutShell,
UsersTab, GroupsTab, RolesTab, and LevelFilterBar into CSS modules.
Follows project convention of CSS modules over inline styles.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/components/LayoutShell.module.css

@@ -0,0 +1,16 @@
+.starredItem {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  padding: 4px 12px;
+  cursor: pointer;
+  font-size: 12px;
+  color: var(--sidebar-text);
+  border-radius: 4px;
+}
+
+.starredParentApp {
+  color: var(--sidebar-muted);
+  margin-left: 4px;
+  font-size: 12px;
+}