Fix the entity IDs in the README and document upgrading

[aurian]

The entity IDs in every example were wrong

The automation and chart examples pointed at entities that do not exist, so pasting one gave an automation that silently never fired.

Every entity sets has_entity_name without device info, so Home Assistant builds the id from the translated entity name and adds no selectra prefix. Verified against a running instance (French):

binary_sensor.marche_planifiee     sensor.prix_actuel      sensor.prix_d_injection
sensor.fournisseur                 sensor.offre            sensor.option

An English instance gets binary_sensor.planned_run / sensor.current_price. Never sensor.selectra_current_price, which is what all seven examples used.

Examples now use the English IDs, and the note above them explains the localization instead of the vague "exact entity IDs depend on your setup". A matching FAQ entry covers the symptom people will actually search for — "my automation does nothing".

Worth a separate discussion: giving the entities a device_info would group them under a device named after the offer and make the ids predictable (sensor.<provider>_<offer>_current_price). That's a code change with its own trade-offs, so it isn't in this PR.

Upgrading is now documented

Updating through HACS doesn't re-run the setup, so the feed-in question added in v1.2.0 never appears on its own. That was only stated in the v1.2.0 release notes, which are buried the moment the next release lands — and the README is what HACS renders on the integration page.

The new section covers the reconfigure path, that the API token isn't asked for again, that the whole qualification re-runs (including periods/strategy), that entities and their history are preserved, and that people without solar panels need do nothing.

Also

• Dropped the "start a discussion" link — Discussions are disabled on this repository, so it led nowhere.
• Caching promoted from an FAQ answer to a Features bullet.

All in-page anchors verified to resolve.

🤖 Generated with Claude Code

https://claude.ai/code/session_01UKLvYuWyejP7VAZ2bxJtMt