Drop self-hosted AI (Ollama + SearXNG); gregtime switches to xAI Grok

The Ollama role and SearXNG container backed FISTO AI responses in the
greg-time Discord bot. greg-time 3.9.6 drops both (plus the Gemini path)
in favor of a single xAI Grok backend, so:

- remove the ollama role and its wiring in deploy_home.yml
- remove the searxng container task, template, and searxng_path default
- gregtime: swap OLLAMA_*/SEARXNG_URL/GEMINI_API_KEY env for XAI_API_KEY,
  bump image 3.6.5 -> 3.9.6
- vault: add xai_api_key, drop gemini_api_key

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ansible/roles/podman/tasks/main.yml

@@ -107,14 +107,9 @@
     image: docker.io/graylog/graylog:7.0.1
   tags: debyltech, graylog
 
-- import_tasks: containers/home/searxng.yml
-  vars:
-    image: docker.io/searxng/searxng:latest
-  tags: searxng
-
 - import_tasks: containers/home/gregtime.yml
   vars:
-    image: localhost/greg-time-bot:3.6.5
+    image: localhost/greg-time-bot:3.9.6
   tags: gregtime
 
 - import_tasks: containers/home/zomboid.yml