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/collectors/service.ts

@@ -0,0 +1,41 @@
+import type { ServiceWidget } from "@/lib/config/schema";
+import type { ServiceStat, ServiceWidgetResult } from "@/lib/types/service-result";
+import { collectDockerContainer, dockerLimit } from "./docker";
+import { collectGitea } from "./services/gitea";
+import { collectCoolify } from "./services/coolify";
+import { collectImmich } from "./services/immich";
+import { collectN8n } from "./services/n8n";
+import { collectUmami } from "./services/umami";
+import { collectHeadscale } from "./services/headscale";
+
+function collectServiceStat(widget: ServiceWidget): Promise<{ stats: ServiceStat[]; detail?: string[] }> {
+  switch (widget.service) {
+    case "gitea":
+      return collectGitea(widget);
+    case "coolify":
+      return collectCoolify(widget);
+    case "immich":
+      return collectImmich(widget);
+    case "n8n":
+      return collectN8n(widget);
+    case "umami":
+      return collectUmami(widget);
+    case "headscale":
+      return collectHeadscale(widget);
+  }
+}
+
+export async function collectService(widget: ServiceWidget): Promise<ServiceWidgetResult> {
+  const dockerPromise = dockerLimit(() => collectDockerContainer(widget.containerName, widget.showStats));
+
+  // A failed service-API call (bad token, service down) must not take out the
+  // docker health readout too - the two are independent failure modes and
+  // merging them into one card should not let one mask the other.
+  const statPromise = collectServiceStat(widget).catch((err) => ({
+    stats: [] as ServiceStat[],
+    statError: (err as Error).message,
+  }));
+
+  const [docker, statResult] = await Promise.all([dockerPromise, statPromise]);
+  return { docker, ...statResult };
+}