## Description
Contact export builds its CSV with the standard library `CSV`, which
writes user-supplied values (name, email, phone, custom attributes)
verbatim. When a cell begins with a formula character (`=`, `+`, `-`,
`@`, and tab/CR), spreadsheet applications interpret it as a formula on
open. This switches the export to `CSVSafe` (the `csv-safe` gem already
used by the v2 report exports), which prefixes such fields so they are
treated as text.
No new dependency, no behavioural change beyond neutralising
formula-leading cells. Note: phone numbers stored with a leading `+` are
now prefixed with a single quote in the exported file, consistent with
how the report exports already behave.
Ref https://linear.app/chatwoot/issue/CW-7473
## Type of change
- [x] Bug fix (non-breaking change which fixes an issue)
## How Has This Been Tested?
`bundle exec rspec spec/jobs/account/contacts_export_job_spec.rb` —
added a case asserting a formula-leading contact value is neutralised on
export; existing cases updated for the phone-number prefix.
## Checklist:
- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
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