v1.0.0

First public release. A Ruby port of the official SMS.ru PHP library covering the
same API, reworked to be idiomatic Ruby. How it differs from the original:

• Idiomatic, namespaced API instead of flat get_*/add_* methods: account
  reads under client.my (#balance, #limit, #free_limit, #senders),
  credential check via client.auth.ok?, plus client.stoplist,
  client.callbacks, and client.callcheck sub-resources. Keyword arguments for
  every optional send parameter, plus a per-client from default.
• Typed, immutable Data results that separate operation outcome from
  delivery state: #ok? plus #error_code/#error_text on rejected
  Sms/CostItem entries; #delivered?/#pending?/#failed?/#found? and
  named SmsRu::Statuses constants for the delivery status_code on Status
  and webhook events; #ok?/#ok/#failed collection helpers on SendResult
  and Cost; plus #confirmed? and #available_today. No raw decoded JSON or
  magic numbers.
• Typed error hierarchy under SmsRu::Error (AuthError,
  InsufficientFundsError, ResponseError, ConnectionError) — errors are
  raised, not returned as status codes you have to inspect.
• First-class inbound webhooks: SmsRu::Webhook.parse decodes the callback
  POST into typed events (SmsRu::Events::SmsStatus, CallcheckStatus, Test,
  Unknown), and SmsRu::Webhook.valid? verifies the signature.
• Zero runtime dependencies (Ruby stdlib only, no curl), TLS verified by
  default, with configurable timeout, retries, global test mode, and an
  optional logger.
• Ships RBS type signatures (sig/) checked at 100% coverage under Steep's
  strict profile and verified against the test suite at runtime (rbs test);
  SMS.ru's loosely-typed JSON is normalized to the declared types at the parse
  boundary, so result objects never surface raw wire values.