## Description
The CSAT survey response CSV export builds rows with the standard
library `CSV`, writing values verbatim, including the feedback message,
which is free text submitted by end users. When a cell begins with a
formula character (`=`, `+`, `-`, `@`, and tab/CR), spreadsheet
applications interpret it as a formula on open. This switches the three
`CSV.generate_line` calls in the export template to
`CSVSafe.generate_line` (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.
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/controllers/api/v1/accounts/csat_survey_responses_controller_spec.rb`
— added a case asserting a formula-leading feedback value is neutralised
in the downloaded CSV.
## 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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