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/services/umami.ts

@@ -0,0 +1,48 @@
+import type { UmamiServiceWidget } from "@/lib/config/schema";
+import type { ServiceStat } from "@/lib/types/service-result";
+import { serviceBaseUrl } from "./base-url";
+
+// Self-hosted Umami has no static API-key header (that's Cloud-only) - it needs
+// a username/password login exchanged for a Bearer token. Cache the token per
+// container and only re-login when a request comes back 401, since the docs
+// don't document a fixed token lifetime to pre-emptively refresh against.
+const tokenCache = new Map<string, string>();
+
+async function login(widget: UmamiServiceWidget, base: string): Promise<string> {
+  const response = await fetch(`${base}/api/auth/login`, {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify({ username: widget.username, password: widget.password }),
+    signal: AbortSignal.timeout(5_000),
+  });
+  if (!response.ok) {
+    throw new Error(`Umami login returned ${response.status}`);
+  }
+  const body = (await response.json()) as { token: string };
+  tokenCache.set(widget.containerName, body.token);
+  return body.token;
+}
+
+export async function collectUmami(widget: UmamiServiceWidget): Promise<{ stats: ServiceStat[] }> {
+  const base = serviceBaseUrl(widget);
+  let token = tokenCache.get(widget.containerName) ?? (await login(widget, base));
+
+  let response = await fetch(`${base}/api/websites/${widget.websiteId}/active`, {
+    headers: { Authorization: `Bearer ${token}` },
+    signal: AbortSignal.timeout(5_000),
+  });
+
+  if (response.status === 401) {
+    token = await login(widget, base);
+    response = await fetch(`${base}/api/websites/${widget.websiteId}/active`, {
+      headers: { Authorization: `Bearer ${token}` },
+      signal: AbortSignal.timeout(5_000),
+    });
+  }
+
+  if (!response.ok) {
+    throw new Error(`Umami API returned ${response.status}`);
+  }
+  const body = (await response.json()) as { visitors: number };
+  return { stats: [{ label: "Active", value: String(body.visitors) }] };
+}