feat: add configurable flow retention settings with super admin controls and pagination for workload flows

Add RuntimeSettingsRead/RuntimeSettingsUpdate schemas with flow_retention_hours field (1-8760 hours), implement runtime_setting helper to initialize/fetch runtime system setting with 24h default, add require_super_admin guard to validate * permission, update agent_heartbeat to use configurable retention_cutoff from runtime settings instead of hardcoded 24h, replace /settings GET endpoint to return RuntimeSettingsRead with flow_retention_hours,

frontend/src/App.tsx

@@ -16,6 +16,7 @@ import { Policies } from "./pages/Policies";
 import { PolicyDesigner } from "./pages/PolicyDesigner";
 import { SecurityGroups } from "./pages/SecurityGroups";
 import { ServiceCatalog } from "./pages/ServiceCatalog";
+import { Settings } from "./pages/Settings";
 import { SetupWizard } from "./pages/SetupWizard";
 import { TenantsProjects } from "./pages/TenantsProjects";
 import { UsersRoles } from "./pages/UsersRoles";
@@ -62,7 +63,7 @@ function AppRoutes() {
         <Route path="jobs" element={<ListPage title="Jobs" subtitle="Background task state and execution logs." path="/jobs" columns={[{ key: "kind", label: "Kind" }, { key: "status", label: "Status" }, { key: "progress", label: "Progress" }]} />} />
         <Route path="audit" element={<ListPage title="Audit Logs" subtitle="Security-relevant activity and change history." path="/audit" columns={[{ key: "created_at", label: "Time" }, { key: "action", label: "Action" }, { key: "object_type", label: "Object" }, { key: "result", label: "Result" }]} />} />
         <Route path="users" element={<UsersRoles />} />
-        <Route path="settings" element={<ListPage title="Settings" subtitle="Runtime settings and safety defaults." path="/settings" columns={[{ key: "product", label: "Product" }, { key: "firewall_apply_requires_preview", label: "Preview Required" }, { key: "agent_optional", label: "Agent Optional" }]} />} />
+        <Route path="settings" element={<Settings />} />
       </Route>
     </Routes>
   );