When syncing contacts to LeadSquared, the `Lead.CreateOrUpdate` API
defaults to searching by email. If a contact has no email (or a
different email) but a phone number matching an existing lead, the API
fails with `MXDuplicateEntryException` instead of finding and updating
the existing lead. This accounted for ~69% of all LeadSquared
integration errors, and cascaded into "Lead not found" failures when
posting transcript and conversation activities (~14% of errors).
## What changed
- `LeadClient#create_or_update_lead` now catches
`MXDuplicateEntryException` and retries the request once with
`SearchBy=Phone` appended to the body, telling the API to match on phone
number instead
- Once the retry succeeds, the returned lead ID is stored on the contact
(existing behavior), so all future events use the direct `update_lead`
path and never hit the duplicate error again
## How to reproduce
1. Create a lead in LeadSquared with phone number `+91-75076767676` and
email `a@example.com`
2. In Chatwoot, create a contact with the same phone number but a
different email (or no email)
3. Trigger a contact sync (via conversation creation or contact update)
4. Before fix: `MXDuplicateEntryException` error in logs, contact fails
to sync
5. After fix: retry with `SearchBy=Phone` finds and updates the existing
lead, stores the lead ID on the contact
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