v0.5.0 — Multi-provider architecture

v0.5.0 — Multi-provider architecture

Major refactor: geely-charger-ha renamed to evse-hub-ha, HA domain
renamed to evse_hub. Introduces a Provider SPI + unified data models
so future vendors can be added by writing a single provider//
package.

Highlights:

• Provider ABC + @register_provider registry
• Unified Equipment / ChargeStatus / TokenBundle / Health / Versions
• switch / sensor / binary_sensor entities are now provider-agnostic
• Config flow picks provider first (auto-skipped when only one is bundled)
• docs/PROVIDER-GUIDE.md contributor guide
• tests/ + CI on push/PR

Breaking:

• HA integration domain changed geely_charger -> evse_hub
• Existing 0.4.0 users must re-add the integration once after upgrade