feat(captain): add FAQ suggestion review API (3/4) (#14979)

Agents can review recurring FAQ suggestions when they can access at
least one supporting conversation. The detail view returns only source
conversations the agent can access. Administrators can review every
suggestion and can edit, approve, or dismiss it. Approval creates one
approved Captain FAQ and removes the stored source observations.

This is the third PR in the CW-7495 stack. It is built on
[#14978](https://github.com/chatwoot/chatwoot/pull/14978), which adds
the FAQ suggestion models and generation flow.

## Closes

Closes
[CW-7495](https://linear.app/chatwoot/issue/CW-7495/backend-llm-changes-to-make-conversation-faqs-as-signalssuggestions).

## What changed

1. Added a paginated suggestion list with assistant, status, and search
filters.
2. Limited agents to suggestions that have at least one source
conversation they can access.
3. Limited the detail response to the 50 most recent source
conversations the current user can access.
4. Allowed administrators to edit, approve, and dismiss open
suggestions.
5. Added approval that creates one approved Captain FAQ, closes the
suggestion, and removes its source observations.
6. Rejected approval when the suggestion language does not match the
account language.
7. Added row locking so an edit or dismissal cannot overwrite an
approval.
8. Prevented FAQ generation from attaching a new observation after a
suggestion has closed.

## How to test

1. Sign in as an agent who has access to one inbox but not another.
2. Confirm the agent sees only suggestions with at least one source
conversation from an accessible inbox.
3. Open a suggestion and confirm the source list does not contain
conversations from restricted inboxes.
4. Sign in as an administrator and confirm all account suggestions are
available.
5. Edit an open suggestion and approve it. Confirm one approved FAQ is
created and the suggestion no longer has source observations.
6. Try to approve a suggestion in a different language from the account
language. Confirm the request is rejected.
7. Dismiss another open suggestion and confirm it leaves the open review
queue.

---------

Co-authored-by: Sony Mathew <sony@chatwoot.com>
Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>

config/routes.rb

@@ -79,6 +79,10 @@ Rails.application.routes.draw do
             end
             resources :agent_sessions, only: [:show]
             resources :assistant_responses
+            resources :faq_suggestions, only: [:index, :show, :update] do
+              post :approve, on: :member
+              post :dismiss, on: :member
+            end
             resources :message_reports, only: [:create]
             resources :bulk_actions, only: [:create]
             resources :copilot_threads, only: [:index, :create] do