Send OctoEverywhere alerts to Google Chat instead of Notify.Events

Replace the Notify.Events delivery with a Google Chat space webhook. The
automation builds a cardsV2 card (printer/event header, print details,
camera snapshot, Open printer button) and falls back to plain text if
Google rejects the card or the request fails.

Adds rest_command.google_chat_octoeverywhere, which needs
google_chat_octoeverywhere_webhook in secrets.yaml on the host. The
notify_event_octoeverywhere_token secret is no longer used.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

helpers/rest_command.yaml

@@ -35,3 +35,12 @@ notion_update_print:
         "date:Completed:start": { "date": { "start": "{{ completed }}", "time_zone": "America/New_York" } }
       }
     }
+
+# Google Chat incoming webhook (space webhook) for OctoEverywhere printer alerts.
+# Call with `payload` = a dict shaped like a Chat Message body (text and/or cardsV2).
+# Used by automations/05_printers_and_workshop/05c_octoeverywhere_google_chat.yaml.
+google_chat_octoeverywhere:
+  url: !secret google_chat_octoeverywhere_webhook
+  method: POST
+  content_type: "application/json; charset=UTF-8"
+  payload: "{{ payload | to_json }}"