feat(homeassistant): its page offers the metrics scrape under the same sign-in, so one user covers everything (#6744)

A Prometheus target's token_from names the plugin that supplies its token at each
scrape. Read its metrics makes the target; Use this sign-in moves one at that address
across, keeping its name, filters and history. A refusal stops the connection, so one
Try again or sign-in starts everything, and the sign-in is only sent to its own address.
A 404 says how to turn on Home Assistant's Prometheus integration, as Steward doesn't
change Home Assistant. Refused also joins the volatile columns a backup check ignores.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

plugins/homeassistant/client.py

@@ -118,6 +118,12 @@ async def redeem_code(url: str, client_id: str, code: str, verify_tls: bool, tra
     return refresh_token, _remember(refresh_token, found)
 
 
+def forget_access() -> None:
+    """Drop access tokens made so far: after a refusal the next ask starts from the
+    sign-in, which a dead user is refused at without counting toward a ban."""
+    _access.clear()
+
+
 async def access_token(connection, transport=None) -> str:
     refresh_token = decrypt_secret(connection.refresh_token, context="Home Assistant sign-in")
     token, until = _access.get(refresh_token, (None, 0.0))