fix: drop the URL from the base_url description for hassfest

The LAN-address scrub replaced 10.10.70.133 with litellm.local in
strings.json, which broke the hassfest job that had been green:

  [ERROR] [TRANSLATIONS] Invalid strings.json: the string should not
  contain URLs, please use description placeholders instead at
  'config.step.user.data_description.base_url'

The rule is not new -- the previous text was equally a URL. It slipped
through because script/hassfest/translations.py's RE_URL requires an
alphabetic TLD ([a-z]{2,5}), so "http://10.10.70.133:4000/v1" never
matched (".133" is not alphabetic) while "http://litellm.local:4000/v1"
does. Verified by running core's actual regex against both strings, so
the scrub did not introduce a violation so much as stop hiding one.

Rather than wire up a description placeholder for what is only an
example, the description now describes the field without any URL:
concrete endpoint examples live in the README, which has no such
constraint. The reauth_confirm step picks this up automatically -- it
references the user step's strings via [%key:...%] rather than copying
them.

Also re-ran core's RE_URL over every string in strings.json, not just
the one hassfest named: 0 remaining violations, so this should not
bounce again on a second string.

Local: 138 passed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NxJYWgGJtCw13qUHZtG8ki

custom_components/openai_compatible/strings.json

@@ -30,7 +30,7 @@
         },
         "data_description": {
           "api_key": "Your OpenAI API key.",
-          "base_url": "The OpenAI-compatible endpoint, e.g. http://litellm.local:4000/v1 for LiteLLM. Must support the Responses API."
+          "base_url": "The base URL of the OpenAI-compatible API, including any version path such as /v1. The endpoint must implement the Responses API."
         },
         "description": "Set up OpenAI Conversation integration by providing your OpenAI API key. Instructions to obtain an API key can be found [here]({instructions_url})."
       }