feat: show processing status for one-off campaigns (#14592)

## Summary

One-off SMS and WhatsApp campaigns now show a `Processing` state while
the audience send is in progress. The campaign moves to `Completed`
after processing finishes, and already-processing campaigns are skipped
by the scheduler to avoid duplicate sends.

## Closes

- [CW-6037: feat: Introduce an in-progress status for
campaigns](https://linear.app/chatwoot/issue/CW-6037/feat-introduce-an-in-progress-status-for-campaigns)

## Screenshot

SMS campaign card showing the new `Processing` status.

<img width="3840" height="2160" alt="framed-campaign-processing-status"
src="https://github.com/user-attachments/assets/de7913b5-65fb-4121-9034-24a568eb0382"
/>

## What changed

- Added `processing` as a campaign status.
- Mark one-off campaigns as `processing` under a row lock before the
send service runs.
- Complete SMS, Twilio SMS, and WhatsApp one-off campaigns after
audience processing finishes.
- Keep campaigns in `processing` if an unexpected service error escapes,
so the scheduler does not automatically resend the audience.
- Added the `Processing` label for SMS and WhatsApp campaign cards.

## Known operational behavior

If a worker is interrupted or an unexpected service error escapes after
a campaign is marked `processing`, the campaign can remain in
`processing`. This is intentional for now to avoid automatic
full-audience resends. Installation admins can decide whether to mark
the campaign completed or restart it manually from the Rails console
after checking what was sent.

## How to test

- Create a one-off SMS or WhatsApp campaign scheduled for now.
- Run the scheduled job or trigger the campaign job.
- Confirm the campaign card shows `Processing` while the audience is
being processed. For small audiences, refresh during processing or use a
larger audience so the state is observable.
- Confirm the campaign moves to `Completed` after audience processing
finishes.
- Confirm an already-processing campaign is not enqueued again by the
scheduled job.

app/models/campaign.rb

@@ -47,7 +47,7 @@ class Campaign < ApplicationRecord
 
   enum campaign_type: { ongoing: 0, one_off: 1 }
   # TODO : enabled attribute is unneccessary . lets move that to the campaign status with additional statuses like draft, disabled etc.
-  enum campaign_status: { active: 0, completed: 1 }
+  enum campaign_status: { active: 0, completed: 1, processing: 2 }
 
   has_many :conversations, dependent: :nullify, autosave: true
 
@@ -56,13 +56,27 @@ class Campaign < ApplicationRecord
 
   def trigger!
     return unless one_off?
-    return if completed?
+    return unless feature_enabled?
+    return unless mark_processing!
 
     execute_campaign
   end
 
   private
 
+  def feature_enabled?
+    inbox.inbox_type != 'Whatsapp' || account.feature_enabled?(:whatsapp_campaign)
+  end
+
+  def mark_processing!
+    # Multiple scheduler jobs can pick the same active campaign; lock before flipping status to avoid duplicate sends.
+    with_lock do
+      next if completed? || processing?
+
+      processing!
+    end
+  end
+
   def execute_campaign
     case inbox.inbox_type
     when 'Twilio SMS'
@@ -70,7 +84,7 @@ class Campaign < ApplicationRecord
     when 'Sms'
       Sms::OneoffSmsCampaignService.new(campaign: self).perform
     when 'Whatsapp'
-      Whatsapp::OneoffCampaignService.new(campaign: self).perform if account.feature_enabled?(:whatsapp_campaign)
+      Whatsapp::OneoffCampaignService.new(campaign: self).perform
     end
   end