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/store/modules/specs/assignmentPolicies/fixtures.js

@@ -0,0 +1,57 @@
+export default [
+  {
+    id: 1,
+    name: 'Round Robin Policy',
+    description: 'Distributes conversations evenly among agents',
+    assignment_order: 'round_robin',
+    conversation_priority: 'earliest_created',
+    fair_distribution_limit: 100,
+    fair_distribution_window: 3600,
+    enabled: true,
+    assigned_inbox_count: 3,
+    created_at: 1704110400,
+    updated_at: 1704110400,
+  },
+  {
+    id: 2,
+    name: 'Balanced Policy',
+    description: 'Assigns conversations based on agent capacity',
+    assignment_order: 'balanced',
+    conversation_priority: 'longest_waiting',
+    fair_distribution_limit: 50,
+    fair_distribution_window: 1800,
+    enabled: false,
+    assigned_inbox_count: 1,
+    created_at: 1704114000,
+    updated_at: 1704114000,
+  },
+];
+
+export const camelCaseFixtures = [
+  {
+    id: 1,
+    name: 'Round Robin Policy',
+    description: 'Distributes conversations evenly among agents',
+    assignmentOrder: 'round_robin',
+    conversationPriority: 'earliest_created',
+    fairDistributionLimit: 100,
+    fairDistributionWindow: 3600,
+    enabled: true,
+    assignedInboxCount: 3,
+    createdAt: 1704110400,
+    updatedAt: 1704110400,
+  },
+  {
+    id: 2,
+    name: 'Balanced Policy',
+    description: 'Assigns conversations based on agent capacity',
+    assignmentOrder: 'balanced',
+    conversationPriority: 'longest_waiting',
+    fairDistributionLimit: 50,
+    fairDistributionWindow: 1800,
+    enabled: false,
+    assignedInboxCount: 1,
+    createdAt: 1704114000,
+    updatedAt: 1704114000,
+  },
+];