feat: add contact filter for conversations (#14629)

# Pull Request Template

## Description

Adds a Contact condition to the conversation advanced filter so agents
can search for an existing contact and filter conversations by
`conversations.contact_id`.

Fixes
[CW-7239](https://linear.app/chatwoot/issue/CW-7239/contact-filter-for-conversations)

## Type of change

- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality not to work as expected)
- [ ] This change requires a documentation update

## How Has This Been Tested?

- `eval "$(rbenv init -)" && bundle exec rspec
spec/services/conversations/filter_service_spec.rb`
- `pnpm exec vitest --no-watch --no-cache --no-coverage --logHeapUsage
app/javascript/dashboard/components-next/filter/helper/filterHelper.spec.js
app/javascript/dashboard/store/modules/conversations/helpers/specs/filterHelpers.spec.js
app/javascript/dashboard/helper/specs/customViewsHelper.spec.js
app/javascript/dashboard/helper/specs/filterQueryGenerator.spec.js`
- `pnpm eslint`
- `eval "$(rbenv init -)" && bundle exec rubocop
spec/services/conversations/filter_service_spec.rb`

## 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
- [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
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: iamsivin <iamsivin@gmail.com>
Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>

app/javascript/dashboard/components-next/NewConversation/helpers/composeConversationHelper.js

@@ -182,7 +182,10 @@ const MIN_SEARCH_LENGTH = 2;
 export const createContactSearcher = () => {
   let controller = null;
 
-  return async (query, { skipMinLength = false } = {}) => {
+  return async (
+    query,
+    { skipMinLength = false, reachableOnly = true } = {}
+  ) => {
     const trimmed = typeof query === 'string' ? query.trim() : '';
 
     controller?.abort();
@@ -199,6 +202,8 @@ export const createContactSearcher = () => {
       } = await ContactAPI.search(trimmed, 1, 'name', '', { signal });
 
       const camelCasedPayload = camelcaseKeys(payload, { deep: true });
+      if (!reachableOnly) return camelCasedPayload || [];
+
       // Filter contacts that have either phone_number or email
       const filteredPayload = camelCasedPayload?.filter(
         contact => contact.phoneNumber || contact.email