feat: Add conversations summary CSV export (#13110)

# Pull Request Template

## Description

This PR adds support for exporting conversation summary reports as CSV.
Previously, the Conversations report incorrectly showed an option to
download agent reports; this has now been fixed to export
conversation-level data instead.

Fixes
https://linear.app/chatwoot/issue/CW-6176/conversation-reports-export-button-exports-agent-reports-instead

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?

### Screenshot
<img width="1859" height="1154" alt="image"
src="https://github.com/user-attachments/assets/419d26f4-fda9-4782-aea6-55ffad0c37ab"
/>



## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [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
- [ ] Any dependent changes have been merged and published in downstream
modules

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

app/helpers/api/v2/accounts/reports_helper.rb

@@ -46,6 +46,13 @@ module Api::V2::Accounts::ReportsHelper
     end
   end
 
+  def generate_conversations_report
+    builder = V2::Reports::Conversations::MetricBuilder.new(Current.account, build_params(type: :account))
+    summary = builder.summary
+
+    [generate_conversation_report_metrics(summary)]
+  end
+
   private
 
   def build_params(base_params)
@@ -71,4 +78,16 @@ module Api::V2::Accounts::ReportsHelper
       report[:resolved_conversations_count]
     ]
   end
+
+  def generate_conversation_report_metrics(summary)
+    [
+      summary[:conversations_count],
+      summary[:incoming_messages_count],
+      summary[:outgoing_messages_count],
+      Reports::TimeFormatPresenter.new(summary[:avg_first_response_time]).format,
+      Reports::TimeFormatPresenter.new(summary[:avg_resolution_time]).format,
+      summary[:resolutions_count],
+      Reports::TimeFormatPresenter.new(summary[:reply_time]).format
+    ]
+  end
 end