Generalize Google Voice sender config

[Pigbibi]

Summary

• rename Google Voice sender config from Gmail-specific names to generic sender email/password
• keep Gmail SMTP as the default transport so the common setup still needs only recipients, sender email, and sender password
• add optional Google Voice channel-scoped SMTP host/port/security overrides for non-Gmail senders

Tests

• PYTHONPATH=src pytest tests/test_google_voice_notifications.py tests/test_strategy_plugins.py
• PYTHONPATH=src ruff check .

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Validate smtp_security before deriving TLS flags

_send_message derives use_starttls/use_ssl by strict equality against two literals, so any unexpected smtp_security value (for example when callers construct StrategyPluginGoogleVoiceSettings(...) directly instead of from_object) disables both TLS modes. In that case the code attempts an unauthenticated/plain SMTP flow on whatever port is set, which can silently break delivery or downgrade transport security instead of falling back to the documented default (ssl). Consider normalizing/validating smtp_security on dataclass construction or adding a safe fallback in _send_message.

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