fix(integrations): restrict Linear/Notion/Shopify hook deletion to admins (#15126)

Non-admin agents could delete an account's Linear, Notion, or Shopify
integration through the dedicated integration endpoints, which — unlike
the generic hooks endpoint — never checked the caller's role. This
restores the intended admin-only boundary for removing an integration.

## Closes
- https://linear.app/chatwoot/issue/CW-7383
- https://linear.app/chatwoot/issue/CW-7384
- https://linear.app/chatwoot/issue/CW-7189

## How to reproduce
As a non-admin **agent**, `DELETE
/api/v1/accounts/:id/integrations/{linear,notion,shopify}` returned
`200` and removed the account-wide integration. After this change it
returns `401` and the integration is preserved; administrators can still
remove it.

## What changed
- Route integration-hook deletion through `HookPolicy` (admin-only) via
a shared `Integrations::BaseController`, matching the generic hooks
controller.

Co-authored-by: Vishnu Narayanan <iamwishnu@gmail.com>

app/controllers/api/v1/accounts/integrations/linear_controller.rb

@@ -1,6 +1,7 @@
-class Api::V1::Accounts::Integrations::LinearController < Api::V1::Accounts::BaseController
+class Api::V1::Accounts::Integrations::LinearController < Api::V1::Accounts::Integrations::BaseController
   before_action :fetch_conversation, only: [:create_issue, :link_issue, :unlink_issue, :linked_issues]
   before_action :fetch_hook, only: [:destroy]
+  before_action :check_authorization, only: [:destroy]
 
   def destroy
     revoke_linear_token