feat(frontend): rules placeholder

frontend/src/components/RulesList.tsx

@@ -200,7 +200,13 @@ const RulesList: Component = () => {
               <Show when={!rules.loading} fallback={
                 <tr><td colspan="4" class="text-center py-4">Loading...</td></tr>
               }>
-                <For each={rules()}>
+                <For each={rules()} fallback={
+                  <tr>
+                    <td colspan="4" class="text-center py-8 text-gray-500">
+                      No rules configured yet. Click "+ New Rule" to create one.
+                    </td>
+                  </tr>
+                }>
                   {(rule) => (
                     <tr>
                       <td class="px-6 py-4 text-sm font-medium text-gray-900">