feat: Agent assignment policy index page with CRUD actions (#12373)

# Pull Request Template

## Description

This PR incudes new Agent assignment policy index page with CRUD
actions.

Fixes
https://linear.app/chatwoot/issue/CW-5570/feat-assignment-policy-index-page-with-actions

## Type of change

- [x] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?

### Loom

https://www.loom.com/share/17ab5ceca4854f179628a3b53f347e5a?sid=cb64e881-57fd-4ae1-921b-7648653cca33

### Screenshots

**Light mode**
<img width="1428" height="888" alt="image"
src="https://github.com/user-attachments/assets/fdbb83e9-1f4f-4432-9e8a-4a8f1b810d31"
/>


**Dark mode**
<img width="1428" height="888" alt="image"
src="https://github.com/user-attachments/assets/f1fb38b9-1150-482c-ba62-3fe63ee1c7d4"
/>
<img width="726" height="495" alt="image"
src="https://github.com/user-attachments/assets/90a6ad55-9ab6-4adb-93a7-2327f5f09c79"
/>


## 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
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] 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/javascript/dashboard/i18n/locale/en/settings.json

@@ -451,6 +451,31 @@
           "Add agents to a policy - one policy per agent"
         ]
       }
+    },
+    "AGENT_ASSIGNMENT_POLICY": {
+      "INDEX": {
+        "HEADER": {
+          "TITLE": "Assignment policy",
+          "CREATE_POLICY": "New policy"
+        },
+        "CARD": {
+          "ORDER": "Order",
+          "PRIORITY": "Priority",
+          "ACTIVE": "Active",
+          "INACTIVE": "Inactive",
+          "POPOVER": "Added inboxes",
+          "EDIT": "Edit"
+        },
+        "NO_RECORDS_FOUND": "No assignment policies found"
+      },
+      "DELETE_POLICY": {
+        "TITLE": "Delete policy",
+        "DESCRIPTION": "Are you sure you want to delete this policy? This action cannot be undone.",
+        "CONFIRM_BUTTON_LABEL": "Delete",
+        "CANCEL_BUTTON_LABEL": "Cancel",
+        "SUCCESS_MESSAGE": "Assignment policy deleted successfully",
+        "ERROR_MESSAGE": "Failed to delete assignment policy"
+      }
     }
   }
 }