Align Preview and 2.17 specs with what the API sends and accepts (#735)

* Document subscription type retrieval and align field names in Preview and 2.17

- Add GET /subscription_types/{id}
- Use the /contacts/{id}/merge_histories path
- Rename visitor.last_request_at, article_statistics.conversations and conversation_part_metadata.quick_reply_option_uuid
- Use automatic as the sync_behavior value when updating content import sources
- Remove formatted_phone from the 2.17 contact search fields

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

* Align Preview and 2.17 specs with API responses (part 2)

- GET /companies with company_id or name returns a single company
- Preview PUT /companies/{id} documents its request body
- GET /events returns an event list unless summary=true
- POST /events/summaries takes event_summaries as an array, plus id and email
- Getting a missing custom object instance returns 200 with found: false
- 2.17 article create/update accept parent_ids
- Internal article search results are top-level; list items use an integer id
- News items include published_at
- Content snippet availability fields and create defaults corrected
- Conversation teammates, ticket type attribute lists, phone switch,
  SLA status and away status reasons use the actual field names
- 2.17 call transcript returns a JSON array of turns
- IP allowlist endpoints added to Preview
- Preview external pages document audience_ids; contacts include whatsapp_number
- Removed unused AI topics schemas from Preview

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

* Give the Preview update company request body a distinct SDK type name

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

* Accept non-string company custom attributes and null phone statuses

- Company custom attribute values, in the create and update requests and the company response, may be strings (or null), integers, numbers or booleans, not only strings
- Company request size example is now the integer 100
- Update company request documents remote_created_at, matching create-or-update
- associated_to_phone_status enum now includes null, matching the nullable field

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: cathalging