Add ssl_verify config option to fix certificate errors

Raw OpenSSL sockets don't find the system CA bundle the same way Net::HTTP
does. ssl_verify (default: true) is now a config setting that applies to
both HTTP REST calls and WebSocket connections. Set via `portainer-cli configure`.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/portainer_cli/commands/exec.rb

@@ -36,7 +36,7 @@ module PortainerCli
         send_resize(endpoint_id, exec_id) if $stdout.tty?
         trap('SIGWINCH') { send_resize(endpoint_id, exec_id) } if $stdout.tty?
 
-        WebsocketExec.new(ws_url, @config.auth_header).run
+        WebsocketExec.new(ws_url, @config.auth_header, ssl_verify: @config.ssl_verify).run
 
         $stderr.puts dim("\r\nSession ended.")
       rescue PortainerCli::Client::ApiError => e