feat: add combined docker+API service widgets for gitea/coolify/immich/n8n/umami/headscale

One new `service` widget type (nested discriminated union on `service`)
rather than six, so a single config entry shows both docker container
health and a service-specific stat (repo count, project list, photo
count, workflow count, active users, users/nodes) - avoiding the
overhead of configuring a docker widget and a separate service widget
per container. All six collectors hit the service's container name +
internal port directly on falcon_network, the same container-to-
container pattern just proven out for Traefik's own API, avoiding
vpn-only/hairpin-NAT entirely.

Also adds the public/private config split that was scoped in the
original project plan but never built: lib/config/public.ts strips
apiToken/apiKey/password fields before the config reaches the browser
via SSR or the WS config topic - required before any widget could
carry a real secret. Verified via a throwaway secret field that it's
absent from both the SSR HTML and the WS config:update frame.

Endpoint shapes verified live against the running gitea/coolify/immich/
n8n/umami/headscale containers before committing (unauthenticated
requests correctly 401/200 on every target route; gitea's
X-Total-Count header confirmed present).

lib/config/public.ts

@@ -0,0 +1,19 @@
+import type { Config, Widget } from "./schema";
+
+const SECRET_WIDGET_FIELDS = ["apiToken", "apiKey", "password"] as const;
+
+export function toPublicConfig(config: Config): Config {
+  return {
+    ...config,
+    groups: config.groups.map((group) => ({
+      ...group,
+      widgets: group.widgets.map(redactWidget),
+    })),
+  };
+}
+
+function redactWidget(widget: Widget): Widget {
+  const clone: Record<string, unknown> = { ...widget };
+  for (const key of SECRET_WIDGET_FIELDS) delete clone[key];
+  return clone as Widget;
+}