fix: Consider business hours when computing SLA breaches (#13392)

- Fixes SLA breach computation to respect the "Only during business
hours" setting
- Backend now pre-computes SLA deadlines, simplifying frontend logic

## How it works

Before: SLA deadlines were calculated using wall-clock time, ignoring
business hours.

After: When an SLA policy has "Only during business hours" enabled and
the inbox has working hours configured, the deadline is calculated by
adding threshold time only during business hours.


**How you check if a conversation has a SLA hit or miss?**

<img width="474" height="510" alt="Screenshot 2026-01-28 at 7 06 53 PM"
src="https://github.com/user-attachments/assets/54ec8581-18b8-45c6-a356-de8c778ea78d"
/>


**Example:**
- Conversation created: Friday 4:30 PM
- FRT threshold: 1 hour
- Business hours: Mon-Fri 9 AM - 5 PM

| | Breach time |
|--|--|
| Before | Friday 5:30 PM |
| After | Monday 9:30 AM |

## Test plan

- [x] Create an SLA policy with "Only during business hours" enabled
- [x] Configure inbox with business hours (e.g., Mon-Fri 9-5)
- [x] Conversation created during business hours
  - Create a conversation on Wednesday 10:00 AM UTC
- Expected: FRT deadline shows Wednesday 12:00 PM UTC (2 business hours
later)
- [x] Conversation created before business hours
  - Create a conversation on Wednesday 7:00 AM UTC
- Expected: FRT deadline shows Wednesday 11:00 AM UTC (counting starts
at 9 AM)
- [x] Conversation created after business hours
  - Create a conversation on Wednesday 6:00 PM UTC
- Expected: FRT deadline shows Thursday 11:00 AM UTC (counting starts
next day 9 AM)
- [x] Conversation created on weekend
  - Create a conversation on Saturday 10:00 AM UTC
  - Expected: FRT deadline shows Monday 11:00 AM UTC (skips weekend)
- [x] Threshold spans weekend
  - Create a conversation on Friday 4:00 PM UTC with 2-hour FRT
- Expected: FRT deadline shows Monday 10:00 AM UTC (1h Friday + 1h
Monday)
- [x] SLA without business hours
  - Create an SLA policy with only_during_business_hours: false
  - Create a conversation on Friday 4:00 PM UTC with 2-hour FRT
  - Expected: FRT deadline shows Friday 6:00 PM UTC (wall-clock time)
- [x] All Day marked as closed_all_day
  - Create a conversation on Tuesday 4:00 PM UTC with 2-hour FRT
  - Expected: FRT deadline shows Thursday 10:00 AM UTC
- [x] All Day marked as open_all_day
  - Create a conversation on Saturday 10:00 AM UTC with 2-hour FRT
  - Expected: FRT deadline shows Saturday 12:00 PM UTC 
- [x] UI displays correct countdown
  - Verify conversation card shows correct SLA timer
  - Verify timer shows flame icon when breached
  - Verify timer shows alarm icon when within threshold
  - Time updates automatically when time passes
- [x] Verify the breach with a different timezone than your local
timezone

---------

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>
Co-authored-by: Sojan Jose <sojan@pepalo.com>
Co-authored-by: Sony Mathew <sony@chatwoot.com>
Co-authored-by: Sony Mathew <2040199+sony-mathew@users.noreply.github.com>

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

@@ -1,7 +1,7 @@
 <script setup>
 import { ref, computed, onMounted, onUnmounted, watch } from 'vue';
 import { useI18n } from 'vue-i18n';
-import { evaluateSLAStatus } from '@chatwoot/utils';
+import { evaluateSLAStatus } from 'dashboard/helper/slaHelper';
 import SLAPopoverCard from './SLAPopoverCard.vue';
 
 const props = defineProps({
@@ -61,6 +61,7 @@ const updateSlaStatus = () => {
   slaStatus.value = evaluateSLAStatus({
     appliedSla: appliedSLA.value,
     chat: props.chat,
+    slaEvents: slaEvents.value || [],
   });
 };