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/javascript/dashboard/components-next/sidebar/SidebarCollapsedPopover.vue

@@ -197,7 +197,10 @@ onMounted(async () => {
                         class="size-4 flex-shrink-0"
                       />
                       <span class="flex-1 truncate">{{ subChild.label }}</span>
-                      <SidebarUnreadBadge :count="subChild.badgeCount" />
+                      <SidebarUnreadBadge
+                        :count="subChild.badgeCount"
+                        :tooltip="subChild.badgeTooltip"
+                      />
                     </button>
                   </li>
                 </ul>
@@ -220,7 +223,10 @@ onMounted(async () => {
                   class="size-4 flex-shrink-0"
                 />
                 <span class="flex-1 truncate">{{ child.label }}</span>
-                <SidebarUnreadBadge :count="child.badgeCount" />
+                <SidebarUnreadBadge
+                  :count="child.badgeCount"
+                  :tooltip="child.badgeTooltip"
+                />
               </button>
             </li>
           </template>