fix(voice): retry ContactInbox lookup on inbound call race

A concurrent WhatsApp message webhook for the same wa_id could win the
(inbox_id, source_id) insert; the call path then re-raised RecordNotUnique
and the outer rescue mislabeled it as a duplicate provider_call_id,
silently dropping the connect. Handle the race inside ensure_contact_inbox!
and drop the now-redundant outer rescue so unrelated unique violations
surface instead of being swallowed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

enterprise/app/services/voice/inbound_call_builder.rb

@@ -46,12 +46,16 @@ class Voice::InboundCallBuilder
   # Always look up by (inbox, source_id) first — that pair has a UNIQUE index, so
   # creating with a colliding source_id under a different contact would raise
   # RecordNotUnique. Reuse the existing ContactInbox (and its contact) when found.
+  # A concurrent message webhook for the same wa_id can win the (inbox_id, source_id)
+  # race; rescue and re-find so the call path doesn't drop the connect.
   def ensure_contact_inbox!
     sid = source_id_for_provider
     existing = inbox.contact_inboxes.find_by(source_id: sid)
     return existing if existing
 
     ContactInbox.create!(contact: ensure_contact!, inbox: inbox, source_id: sid)
+  rescue ActiveRecord::RecordNotUnique
+    inbox.contact_inboxes.find_by!(source_id: sid)
   end
 
   def ensure_contact!

enterprise/app/services/whatsapp/incoming_call_service.rb

@@ -23,8 +23,6 @@ class Whatsapp::IncomingCallService
     return accept_outbound_call(call, payload) if call.outgoing?
 
     Rails.logger.info "[WHATSAPP CALL] Duplicate inbound connect for #{payload[:id]}; ignoring"
-  rescue ActiveRecord::RecordNotUnique
-    Rails.logger.warn "[WHATSAPP CALL] Duplicate provider_call_id received: #{payload[:id]}"
   end
 
   def create_inbound_call(payload)