feat(services): frontend services runtime and widget rebind

PR 3 of 4 for the runtime service registry change.

- Add service + new-shape widget TypeScript types; widgets carry service_id
  + widget_kind (service-bound) or null (built-in).
- Add services API client + TanStack Query hooks; reconcile the widget API
  client/hooks to the new endpoints (remove sources/types; add builtin kinds).
- Add closed frontend service registry (integrations/registry.ts) mirroring the
  backend, with resolveWidget(widget, services) mapping a widget to its
  component + refresh interval.
- Add ServicePage at /services/:serviceType/:serviceId with config view,
  empty-on-edit secret inputs + 'set' badges, enable toggle, delete, and the
  service's widget-kind list.
- Register /services/:serviceType/:serviceId in App.tsx.
- Reconcile the six widget components to refreshIntervalMs + description props;
  rewrite WidgetConfigDialog around a service -> widget-kind picker.
- Update Dashboard test; add integrations/registry.test.ts.

Verification: frontend lint 0 errors, build success, 70 tests passed; backend
ruff clean, 222 tests passed.

frontend/src/App.tsx

@@ -23,6 +23,7 @@ import { Actions } from "./pages/Actions";
 import BackupsPage from "./components/BackupsPage";
 import { ObservabilityPage } from "./components/ObservabilityPage";
 import { AddonPage } from "./pages/AddonPage";
+import { ServicePage } from "./pages/ServicePage";
 import { getOidcConfig, isOidcConfigured, setAccessToken } from "./auth";
 import { fetchAppVersion } from "./api/client";
 import { FRONTEND_VERSION_LABEL } from "./version";
@@ -451,6 +452,7 @@ function AppInner() {
 								<Route path="/observability" element={<ObservabilityPage />} />
 								<Route path="/settings" element={<Settings />} />
 								<Route path="/addons/:addonId" element={<AddonPage />} />
+								<Route path="/services/:serviceType/:serviceId" element={<ServicePage />} />
 							</Route>
 						</Routes>
 					</BrowserRouter>
@@ -483,6 +485,7 @@ function AppInner() {
 							<Route path="/observability" element={<ObservabilityPage />} />
 							<Route path="/settings" element={<Settings />} />
 							<Route path="/addons/:addonId" element={<AddonPage />} />
+							<Route path="/services/:serviceType/:serviceId" element={<ServicePage />} />
 						</Route>
 					</Routes>
 				</BrowserRouter>