fix: V2 Assignment service enhancements (#13036)

## Linear Ticket:
https://linear.app/chatwoot/issue/CW-6081/review-feedback

## Description

Assignment V2 Service Enhancements

- Enable Assignment V2 on plan upgrade
- Fix UI issue with fair distribution policy display
- Add advanced assignment feature flag and enhance Assignment V2
capabilities

## Type of change

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

## How Has This Been Tested?

This has been tested using the 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

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Changes auto-assignment execution paths, rate limiting defaults, and
feature-flag gating (including premium plan behavior), which could
affect which conversations get assigned and when. UI rewires inbox
settings and policy flows, so regressions are possible around
navigation/linking and feature visibility.
> 
> **Overview**
> **Adds a new premium `advanced_assignment` feature flag** and uses it
to gate capacity/balanced assignment features in the UI (sidebar entry,
settings routes, assignment-policy landing cards) and backend
(Enterprise balanced selector + capacity filtering).
`advanced_assignment` is marked premium, included in Business plan
entitlements, and auto-synced in Enterprise accounts when
`assignment_v2` is toggled.
> 
> **Improves Assignment V2 policy UX** by adding an inbox-level
“Conversation Assignment” section (behind `assignment_v2`) that can
link/unlink an assignment policy, navigate to create/edit policy flows
with `inboxId` query context, and show an inbox-link prompt after
creating a policy. The policy form now defaults to enabled, disables the
`balanced` option with a premium badge/message when unavailable, and
inbox lists support click-to-navigate.
> 
> **Tightens/adjusts auto-assignment behavior**: bulk assignment now
requires `inbox.enable_auto_assignment?`, conversation ordering uses the
attached `assignment_policy` priority, and rate limiting uses
`assignment_policy` config with an infinite default limit while still
tracking assignments. Tests and i18n strings are updated accordingly.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
23bc03bf75ee4376071e4d7fc7cd564c601d33d7. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Pranav <pranav@chatwoot.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>
Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>
Co-authored-by: Shivam Mishra <scm.mymail@gmail.com>

enterprise/app/models/enterprise/account.rb

@@ -3,6 +3,12 @@ module Enterprise::Account
   # this is a temporary method since current administrate doesn't support virtual attributes
   def manually_managed_features; end
 
+  # Auto-sync advanced_assignment with assignment_v2 when features are bulk-updated via admin UI
+  def selected_feature_flags=(features)
+    super
+    sync_assignment_features
+  end
+
   def mark_for_deletion(reason = 'manual_deletion')
     reason = reason.to_s == 'manual_deletion' ? 'manual_deletion' : 'inactivity'
 
@@ -31,4 +37,21 @@ module Enterprise::Account
   def saml_enabled?
     saml_settings&.saml_enabled? || false
   end
+
+  private
+
+  def sync_assignment_features
+    if feature_enabled?('assignment_v2')
+      # Enable advanced_assignment for Business/Enterprise plans
+      send('feature_advanced_assignment=', true) if business_or_enterprise_plan?
+    else
+      # Disable advanced_assignment when assignment_v2 is disabled
+      send('feature_advanced_assignment=', false)
+    end
+  end
+
+  def business_or_enterprise_plan?
+    plan_name = custom_attributes['plan_name']
+    %w[Business Enterprise].include?(plan_name)
+  end
 end

enterprise/app/services/enterprise/auto_assignment/assignment_service.rb

@@ -19,7 +19,8 @@ module Enterprise::AutoAssignment::AssignmentService
     agents = filter_agents_by_capacity(agents) if capacity_filtering_enabled?
     return nil if agents.empty?
 
-    selector = policy&.balanced? ? balanced_selector : round_robin_selector
+    # Use balanced selector only if advanced_assignment feature is enabled
+    selector = policy&.balanced? && account.feature_enabled?('advanced_assignment') ? balanced_selector : round_robin_selector
     selector.select_agent(agents)
   end
 
@@ -31,7 +32,7 @@ module Enterprise::AutoAssignment::AssignmentService
   end
 
   def capacity_filtering_enabled?
-    account.feature_enabled?('assignment_v2') &&
+    account.feature_enabled?('advanced_assignment') &&
       account.account_users.joins(:agent_capacity_policy).exists?
   end
 

enterprise/app/services/enterprise/billing/handle_stripe_event_service.rb

@@ -22,7 +22,7 @@ class Enterprise::Billing::HandleStripeEventService
   ].freeze
 
   # Additional features available starting with the Business plan
-  BUSINESS_PLAN_FEATURES = %w[sla custom_roles csat_review_notes conversation_required_attributes].freeze
+  BUSINESS_PLAN_FEATURES = %w[sla custom_roles csat_review_notes conversation_required_attributes advanced_assignment].freeze
 
   # Additional features available only in the Enterprise plan
   ENTERPRISE_PLAN_FEATURES = %w[audit_logs disable_branding saml].freeze