feat: vendor console — tenant list, create wizard, detail page

Implements Task 9: shared components (ServerStatusBadge, UsageIndicator,
platform.module.css, tierColor utility) and full vendor console pages
(VendorTenantsPage, CreateTenantPage, TenantDetailPage). Build passes cleanly.

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

ui/src/components/UsageIndicator.tsx

@@ -0,0 +1,27 @@
+import styles from '../styles/platform.module.css';
+
+interface Props {
+  used: number;
+  limit: number;
+  label: string;
+}
+
+export function UsageIndicator({ used, limit, label }: Props) {
+  const unlimited = limit < 0;
+  const pct = unlimited ? 0 : Math.min((used / limit) * 100, 100);
+  const color = pct >= 100 ? 'var(--error)' : pct >= 80 ? 'var(--warning)' : 'var(--success)';
+
+  return (
+    <div style={{ display: 'flex', flexDirection: 'column', gap: 4 }}>
+      <div className={styles.kvRow}>
+        <span className={styles.kvLabel}>{label}</span>
+        <span className={styles.kvValue}>{used} / {unlimited ? '\u221e' : limit}</span>
+      </div>
+      {!unlimited && (
+        <div style={{ height: 4, borderRadius: 2, background: 'var(--bg-inset)', overflow: 'hidden' }}>
+          <div style={{ width: `${pct}%`, height: '100%', borderRadius: 2, background: color, transition: 'width 0.3s' }} />
+        </div>
+      )}
+    </div>
+  );
+}