feat(homeassistant): it shows system problems and installs updates on a weekly slot, and leaves device readings alone (#6748, #6749, #6747)

The connection's job is keeping Home Assistant running. Each poll now reads open
repairs, Supervisor health, disk, recovery mode and add-ons that should be running
over its websocket, for the page, the overview and the problems_open, disk_free_pct
and update_failed metrics. That needs a websocket client, so websockets joins the
dependencies.

A weekly slot, set on the page or through MCP and off until then, installs add-ons,
then Core, then the OS, each after its own confirmed backup, ending at the first
failure. The slot arithmetic moves from the host agent's cadence to steward.core.weekly
so both share it.

The device scrape goes: the page's Metrics section and a target's token_from from
4c9ed02 are removed, and a migration deletes targets using it, as they'd otherwise ask
with no token. A refused token still stops a scrape.

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

plugins/prometheus/models.py

@@ -13,8 +13,7 @@ from steward.models.base import Base
 class PrometheusTarget(Base):
     """A /metrics endpoint Steward scrapes, edited on the Prometheus page.
 
-    The bearer token is stored encrypted, or `token_from` names the plugin whose
-    sign-in supplies it at each scrape (its metrics.scrape_token). keep and drop are lists of name
+    The bearer token is stored encrypted. keep and drop are lists of name
     patterns ("fabledarchives_*") an admin chooses: Steward does the
     filtering, the endpoint serves everything. The last_* columns are the
     newest scrape's outcome, written by the scraper, so a page can say why a
@@ -27,7 +26,6 @@ class PrometheusTarget(Base):
     name: Mapped[str] = mapped_column(String(100), nullable=False, unique=True)
     url: Mapped[str] = mapped_column(String(500), nullable=False)
     token: Mapped[str] = mapped_column(Text, nullable=False, default="")
-    token_from: Mapped[str | None] = mapped_column(String(50), nullable=True)
     verify_tls: Mapped[bool] = mapped_column(Boolean, nullable=False, default=True)
     interval_seconds: Mapped[int] = mapped_column(Integer, nullable=False, default=60)
     keep: Mapped[list] = mapped_column(JSON, nullable=False, default=list)