fix: restore token access to account APIs (#15088)

Token-authenticated requests to Agent Bots, Labels, and affected Captain
endpoints return normal responses again. The regression was caused by
duplicate `current_account` callbacks in subclasses moving account
resolution behind the API entitlement check, leaving `Current.account`
unset.

## Closes

- https://linear.app/chatwoot/issue/CW-7641/5xx-errors-in-agent-bot-apis

## How to reproduce

1. Send `GET /api/v1/accounts/:account_id/agent_bots` with a valid
administrator API access token.
2. Observe a `500` from `validate_token_api_access` because
`Current.account` is `nil`.
3. With this change, account resolution runs in the base-controller
order and the request succeeds.

## What changed

- Removed redundant `current_account` callbacks from account-scoped
controllers that already inherit the callback from
`Api::V1::Accounts::BaseController`.
- Kept the standalone direct-upload controller callback unchanged.
- Added regression coverage for administrator API-token access to Agent
Bots.

spec/controllers/api/v1/accounts/agent_bots_controller_spec.rb

@@ -64,6 +64,14 @@ RSpec.describe 'Agent Bot API', type: :request do
         expect(response).to have_http_status(:success)
         expect(response.body).to include(agent_bot.access_token.token)
       end
+
+      it 'supports API token authentication' do
+        get "/api/v1/accounts/#{account.id}/agent_bots",
+            headers: { api_access_token: admin.access_token.token },
+            as: :json
+
+        expect(response).to have_http_status(:success)
+      end
     end
   end