chore: Automate SSL with Cloudflare (#12021)

This PR adds support for automatic SSL issuance using Cloudflare when a
custom domain is updated.

- Introduced a cloudflare configuration. If present, the system will
attempt to issue an SSL certificate via Cloudflare whenever a custom
domain is added or changed.
- SSL verification is handled using an HTTP challenge.
- The job will store the HTTP challenge response provided by Cloudflare
and serve it under the /.well-known/cf path automatically.

How to test:

- Create a Cloudflare zone for your domain and copy the Zone ID.
- Generate a Cloudflare API token with the required SSL certificate
permissions.
- Set the Fallback Origin under SSL -> Custom HostName to the Chatwoot
installation.
- Add or update a custom domain and verify that the SSL certificate is
automatically issued.

---------

Co-authored-by: Sojan Jose <sojan@pepalo.com>

db/migrate/20250722083820_add_ssl_settings_to_portals.rb

@@ -0,0 +1,5 @@
+class AddSslSettingsToPortals < ActiveRecord::Migration[7.1]
+  def change
+    add_column :portals, :ssl_settings, :jsonb, default: {}, null: false
+  end
+end