Replace Clay with n8n, Ollama, SearXNG and browserless; add Telegram assistant

Remove the Clay role (Claude Code web UI) and its Anthropic API key.

New roles:
- ollama: local CPU LLM (qwen3:4b-instruct), internal network only
- browserless: headless Chromium for JavaScript-heavy pages
- searxng: metasearch backend for the chat web_search tool
- n8n at agent.ladkau.de: web chat (/chat), scheduled workflows,
  Telegram bot; workflows and credentials are imported from the repo

Telegram bot: Gemini 3.8 -> Gemini 3.5 -> local Qwen fallback chain,
/qwen to force the local model, /stocks and a weekday schedule
(07:30, 13:00, 17:40) for the MTE.DE / PTX.F stock report.

Also: dashboard and check-services entries for the chat, vault checks
for the new secrets (n8n, SearXNG, Gemini, Telegram, SMTP), updated
CLAUDE.md, runbooks and README.

ansible/roles/dashboard/templates/app.py.j2

@@ -25,7 +25,8 @@ SERVICES = [
     ("k8s",          "https://{{ domain_k8s }}",                200, "https://{{ domain_k8s }}"),
     ("Vaultwarden",  "https://{{ domain_vault }}",             200, "https://{{ domain_vault }}"),
     ("Downloads",    "https://{{ domain_dl }}",               200, "https://{{ domain_dl }}"),
-    ("Clay",         "https://{{ domain_clay }}",             401, "https://{{ domain_clay }}"),
+    ("AI Chat",      "https://{{ domain_n8n }}/chat",         401, "https://{{ domain_n8n }}/chat"),
+    ("n8n",          "https://{{ domain_n8n }}",              401, "https://{{ domain_n8n }}"),
 ]
 {% raw %}