Translation Manager: opt-in Polly retry pipeline for machine connectors

Jumoo.TranslationManager: added an opt-in Polly resilience pipeline to MachineConnectorBase<TOptions> — off by default (UseRetryPolicy), wraps the realtime Translate() call and exposes ExecuteWithResilienceAsync so connectors can reuse it for their own calls (e.g. batch upload/status); BuildResiliencePipeline is virtual so each connector classifies its own API's transient failures instead of one generic policy for all — Jumoo/Jumoo.TranslationManager#39
Jumoo.TranslationManager.DeepL: wired the new pipeline into DeepLConnector, retrying only TooManyRequestsException (rate limit) and ConnectionException (transport failure) with exponential backoff — Jumoo/Jumoo.TranslationManager.Connector.DeepL#18
removed DeepL's manual throttle setting from its config page and hard-coded Throttle to 0, since the retry policy now handles rate limiting instead