feat: Add sidebar unread counts for filters (CW-7262) (#14726)

## Description

Extends the conversation unread-count system so the left sidebar can
show unread badges for Mentions, Participating, Unattended, and saved
conversation folders. Folder badges reuse the existing `custom_filters`
conversation filter semantics, store user-scoped Redis sets lazily, and
skip unsupported folder filters so invalid saved folders continue to
render without a badge. The Unattended badge counts all visible unread
open conversations that match the existing unattended conversation
scope.

Closes
-
[CW-7262](https://linear.app/chatwoot/issue/CW-7262/unread-counts-for-filters-folders)

## What changed

- Added user-scoped unread-count Redis keys and cache builders for
mentions, participating conversations, unattended conversations, and
saved folder filters.
- Reused `Conversations::FilterService` through a relation-returning
path so folder counts match the folder conversation list behavior.
- Invalidated user filter caches from mention, participant,
custom-filter, and relevant conversation update events.
- Extended the unread-count endpoint payload and sidebar Vuex/sidebar
rendering for the new badge counts, including the Unattended sidebar
item.
- Added Ruby, Enterprise, request, listener, and frontend store coverage
for the new unread-count dimensions.

## Type of change

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

## How Has This Been Tested?

- Created local validation folders for `john@acme.inc` and confirmed the
unread-count payload includes open, resolved, and high-priority folder
badges while excluding the invalid unsupported folder.
- Added coverage for the Unattended badge rule: all visible unread open
conversations matching `Conversation.unattended`.
- Ran focused unread-count Ruby specs, including service, listener,
request, and Enterprise counter coverage.
- Ran frontend unread-count store specs.
- Ran RuboCop on the touched Ruby files.
- Ran ESLint through the project script; it completed with warnings in
existing unrelated files and no errors.

<img width="369" height="525" alt="Screenshot 2026-06-13 at 10 51 39 PM"
src="https://github.com/user-attachments/assets/36b1d2c4-dac1-4f6f-9c0e-7ef5a6cc2975"
/>

## 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
- [x] Documentation changes are not required for this internal
unread-count behavior
- [x] My changes generate no new warnings
- [x] 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
- [x] No dependent downstream changes are required

---------

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

app/models/account_user.rb

@@ -39,6 +39,7 @@ class AccountUser < ApplicationRecord
   after_create_commit :notify_creation, :create_notification_setting
   after_destroy :notify_deletion, :remove_user_from_account
   after_save :update_presence_in_redis, if: :saved_change_to_availability?
+  after_commit :notify_unread_filter_counts_changed, on: [:update, :destroy], if: :unread_filter_access_changed?
 
   validates :user_id, uniqueness: { scope: :account_id }
 
@@ -79,6 +80,14 @@ class AccountUser < ApplicationRecord
   def update_presence_in_redis
     OnlineStatusTracker.set_status(account.id, user.id, availability)
   end
+
+  def unread_filter_access_changed?
+    destroyed? || previous_changes.key?('role') || previous_changes.key?('custom_role_id')
+  end
+
+  def notify_unread_filter_counts_changed
+    ::Conversations::UnreadCounts::UserFilterNotifier.new(account: account, user: user).perform
+  end
 end
 
 AccountUser.prepend_mod_with('AccountUser')