feat: distinguish agent-declined calls with a rejected status (#14783)

## Linear ticket
-
https://linear.app/chatwoot/issue/CW-7374/agent-declined-voice-calls-miscounted-as-failed

## Description

Agent rejections were stored with status: failed, so call reports lumped
deliberate declines together with real technical failure.

Fix: give declines their own terminal rejected status (Twilio + WhatsApp
paths), keeping end_reason: agent_rejected. Genuine provider/network
failures stay failed. Frontend renders declines exactly as before;
existing rows backfilled via migration.

## Type of change

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

## How Has This Been Tested?

- Tested on UI

## Checklist:

- [ ] My code follows the style guidelines of this project
- [ ] 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
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Sony Mathew <sony@chatwoot.com>

app/javascript/dashboard/components/widgets/conversation/VoiceCallStatus.vue

@@ -21,6 +21,7 @@ const ICON_MAP = {
   [VOICE_CALL_STATUS.IN_PROGRESS]: 'i-ph-phone-call',
   [VOICE_CALL_STATUS.NO_ANSWER]: 'i-ph-phone-x',
   [VOICE_CALL_STATUS.FAILED]: 'i-ph-phone-x',
+  [VOICE_CALL_STATUS.REJECTED]: 'i-ph-phone-x',
 };
 
 const COLOR_MAP = {
@@ -29,13 +30,18 @@ const COLOR_MAP = {
   [VOICE_CALL_STATUS.COMPLETED]: 'text-n-slate-11',
   [VOICE_CALL_STATUS.NO_ANSWER]: 'text-n-ruby-9',
   [VOICE_CALL_STATUS.FAILED]: 'text-n-ruby-9',
+  [VOICE_CALL_STATUS.REJECTED]: 'text-n-ruby-9',
 };
 
 const isOutbound = computed(
   () => props.direction === VOICE_CALL_DIRECTION.OUTBOUND
 );
 const isFailed = computed(() =>
-  [VOICE_CALL_STATUS.NO_ANSWER, VOICE_CALL_STATUS.FAILED].includes(props.status)
+  [
+    VOICE_CALL_STATUS.NO_ANSWER,
+    VOICE_CALL_STATUS.FAILED,
+    VOICE_CALL_STATUS.REJECTED,
+  ].includes(props.status)
 );
 
 const labelKey = computed(() => {