v1.9.3

A maintenance release: improved missing-key warnings across all providers. No behavior, output, or API changes.

Improvements

Missing or demo API key warnings now include platform-specific instructions for where to add the secret, detected from CI environment variables (GitHub Actions, GitLab CI, CircleCI, Bitbucket Pipelines, Azure Pipelines, Travis CI, Jenkins). Falls back to a generic message on unknown runners or local dev.
Affected providers: EIA (US), Electricity Maps, ENTSO-E (two call sites), and the pre-flight zone notices in the main dispatcher.
The per-provider lookup table in providers/eia.py has been replaced with a shared ci_secret_hint(secret_name) helper in providers/base.py, used by all providers.
ENTSO-E messages replaced Unicode arrow with ASCII -> per project style.