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/templates/searxng/settings.yml.j2

@@ -1,35 +0,0 @@
-use_default_settings: true
-
-general:
-  instance_name: "SearXNG"
-  debug: false
-
-server:
-  bind_address: "127.0.0.1"
-  port: 8080
-  secret_key: "{{ searxng_secret_key }}"
-  limiter: false
-  image_proxy: false
-
-search:
-  safe_search: 0
-  formats:
-    - html
-    - json
-
-engines:
-  - name: duckduckgo
-    engine: duckduckgo
-    disabled: false
-
-  - name: google
-    engine: google
-    disabled: false
-
-  - name: wikipedia
-    engine: wikipedia
-    disabled: false
-
-  - name: bing
-    engine: bing
-    disabled: false