feat(homeassistant): waiting updates, backup age, and updates installed after a confirmed backup (#6355)

A new plugin reads Home Assistant with a read-only token every 5 minutes and
shows which Core, OS and add-on updates are waiting and how old the last backup
is. Install takes a backup through a local-only webhook, confirms Home
Assistant's last-backup time moved, installs, and follows the update to its end,
through Home Assistant's and Steward's own restarts. One runs at a time. Each
ends as one timeline entry.

Steward holds nothing that can act on the house: the webhook's automation can
only take a backup or install an allowed update (System 231's ruling). A refused
token stops polling, as Home Assistant bans an address after a few refusals.

Milestone 576 steps 1 to 5.

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

plugins/homeassistant/models.py

@@ -0,0 +1,68 @@
+# plugins/homeassistant/models.py
+from __future__ import annotations
+
+from datetime import datetime, timezone
+
+from sqlalchemy import JSON, Boolean, DateTime, Index, String, Text, text
+from sqlalchemy.orm import Mapped, mapped_column
+
+from steward.core.ids import time_ordered_id
+from steward.models.base import Base
+
+
+class HomeAssistantConnection(Base):
+    """The Home Assistant instance Steward looks after; at most one row.
+
+    The token is a read-only user's and the webhook id can only reach the
+    maintenance automation, so nothing stored here can act on the house. Both
+    are encrypted. The last_* columns and `updates` and `backup` are the newest
+    poll's outcome, which the pages read. `refused` stops all polling until
+    someone saves the connection or tries again: Home Assistant bans an address
+    after a few refused requests.
+    """
+    __tablename__ = "homeassistant_connection"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=time_ordered_id)
+    url: Mapped[str] = mapped_column(String(500), nullable=False)
+    token: Mapped[str] = mapped_column(Text, nullable=False)
+    webhook_id: Mapped[str] = mapped_column(Text, nullable=False)
+    verify_tls: Mapped[bool] = mapped_column(Boolean, nullable=False, default=True)
+    refused: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
+    last_polled_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
+    last_ok_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
+    last_error: Mapped[str | None] = mapped_column(Text, nullable=True)
+    updates: Mapped[list] = mapped_column(JSON, nullable=False, default=list)
+    backup: Mapped[dict] = mapped_column(JSON, nullable=False, default=dict)
+    automation: Mapped[str | None] = mapped_column(String(20), nullable=True)
+
+
+class HomeAssistantUpdate(Base):
+    """One update Steward was asked to install, from the click to its end. It
+    moves through backing_up and installing to done or failed, and its row
+    carries everything needed to carry on after Steward restarts. The *_before
+    columns are Home Assistant's own readings at the start, so "a newer backup"
+    is judged on its clock alone. One can be under way at a time.
+    """
+    __tablename__ = "homeassistant_updates"
+    __table_args__ = (
+        Index("uq_homeassistant_update_under_way", text("(true)"), unique=True,
+              postgresql_where=text("state IN ('backing_up', 'installing')")),
+    )
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=time_ordered_id)
+    entity_id: Mapped[str] = mapped_column(String(255), nullable=False)
+    title: Mapped[str] = mapped_column(String(255), nullable=False)
+    kind: Mapped[str] = mapped_column(String(10), nullable=False)
+    from_version: Mapped[str | None] = mapped_column(String(100), nullable=True)
+    to_version: Mapped[str | None] = mapped_column(String(100), nullable=True)
+    state: Mapped[str] = mapped_column(String(20), nullable=False, default="backing_up")
+    message: Mapped[str | None] = mapped_column(Text, nullable=True)
+    started_by: Mapped[str] = mapped_column(String(100), nullable=False, default="")
+    started_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False, default=lambda: datetime.now(timezone.utc))
+    backup_before: Mapped[str | None] = mapped_column(String(64), nullable=True)
+    backup_event_before: Mapped[str | None] = mapped_column(String(64), nullable=True)
+    triggered_before: Mapped[str | None] = mapped_column(String(64), nullable=True)
+    backup_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
+    install_sent_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
+    finished_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)