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/widgets/StaticWidget.tsx

@@ -1,19 +1,19 @@
 import { SectionCard } from "../components/SectionCard";
 import { useWidgetData } from "../hooks/useWidgets";
 import type { WidgetInstance } from "../types";
-import { getWidgetDefinition } from "./registry";
 
 interface Props {
 	widget: WidgetInstance;
+	refreshIntervalMs: number;
+	description?: string;
 }
 
-export function StaticWidget({ widget }: Props) {
-	const def = getWidgetDefinition(widget.widget_type);
-	const { data } = useWidgetData(widget.id, def?.refreshInterval ?? 0);
+export function StaticWidget({ widget, refreshIntervalMs, description }: Props) {
+	const { data } = useWidgetData(widget.id, refreshIntervalMs);
 	const text = data?.data?.text as string | undefined;
 
 	return (
-		<SectionCard title={widget.title} description={def?.description}>
+		<SectionCard title={widget.title} description={description}>
 			{text ? (
 				<p className="whitespace-pre-wrap text-sm">{text}</p>
 			) : (