fix: Correct reversed message status indicators for API channel (#13594)

## Description

Fixes the reversed message delivery status indicators for the API
channel. The API inbox was grouped with the web widget inbox in the
`isDelivered` computed property, causing both to treat a `sent` status
as `delivered`. Since the API channel provides real
`sent`/`delivered`/`read` status values from external systems (unlike
the web widget which has no separate delivery confirmation), the API
inbox needs its own handling.

**Before this fix:**
- Status `sent` (0) → incorrectly showed delivered checkmarks
- Status `delivered` (1) → incorrectly showed "Sending" spinner

**After this fix:**
- Status `sent` → correctly shows sent indicator (single checkmark)
- Status `delivered` → correctly shows delivered indicator (double
checkmarks)
- Status `read` → unchanged (already worked correctly)

The web widget inbox behavior is unchanged — it still treats `sent` as
`delivered` since it lacks a separate delivery confirmation mechanism.

Fixes #13576

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)

## How Has This Been Tested?

Verified by code review that the computed properties now correctly map
API channel message statuses:
- `isSent` returns `true` when `status === 'sent'` for API inbox
- `isDelivered` returns `true` when `status === 'delivered'` for API
inbox
- `isRead` unchanged — already checks `status === 'read'` for API inbox
- Web widget inbox logic is unchanged

## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [x] My changes generate no new warnings

*This PR was created with the assistance of Claude Opus 4.6 by
Anthropic. Happy to make any adjustments! Reviewed and submitted by a
human.*

Co-authored-by: Your Name <your-email@example.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

app/javascript/dashboard/components-next/message/MessageMeta.vue

@@ -67,6 +67,9 @@ const isSent = computed(() => {
     return sourceId.value && status.value === MESSAGE_STATUS.SENT;
   }
 
+  // API inbox messages use real sent/delivered/read status values from the external system.
+  if (isAPIInbox.value) return status.value === MESSAGE_STATUS.SENT;
+
   // All messages will be mark as sent for the Line channel, as there is no source ID.
   if (isALineChannel.value) return true;
 
@@ -86,8 +89,10 @@ const isDelivered = computed(() => {
   ) {
     return sourceId.value && status.value === MESSAGE_STATUS.DELIVERED;
   }
-  // All messages marked as delivered for the web widget inbox and API inbox once they are sent.
-  if (isAWebWidgetInbox.value || isAPIInbox.value) {
+  // API inbox messages use real delivered status from the external system.
+  if (isAPIInbox.value) return status.value === MESSAGE_STATUS.DELIVERED;
+  // All messages marked as delivered for the web widget inbox once they are sent.
+  if (isAWebWidgetInbox.value) {
     return status.value === MESSAGE_STATUS.SENT;
   }
   if (isALineChannel.value) {