fix: force JSON output for Ollama intent classification; fix attachment detection

- ollama_backend: add format='json' for 'master' and receipt_parser
  callers so llama3.1:8b returns valid JSON instead of plain English
- ab_ai_mail: add debug logging to trace attachment_ids from Discuss;
  handle file-only messages and clarification look-back flow

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

addons/activeblue_ai/models/ab_ai_mail.py

@@ -84,6 +84,20 @@ class DiscussChannel(models.Model):
             return result
 
         text = _strip_html(body)
+
+        # Odoo 18 Discuss uploads attachments before posting the message and
+        # passes their IDs in kwargs as attachment_ids (list of ints or ORM
+        # commands).  result.attachment_ids resolves those after super() runs.
+        # Log both so we can see exactly what arrives.
+        _logger.info(
+            'AB AI mail hook: body=%r kwargs_keys=%s '
+            'attachment_ids_kwarg=%r result.attachment_ids=%s',
+            (body or '')[:80],
+            list(kwargs.keys()),
+            kwargs.get('attachment_ids'),
+            result.attachment_ids.ids,
+        )
+
         attachments = result.attachment_ids
 
         # Nothing to work with