feat(docker): docker_logs table + docker_009 migration [M79 step 2]

Dedicated host-scoped table for pushed container log lines (one row per line),
chained after docker_008. host_id FK CASCADE; twin indexes — (host_id,
container_name, ts) for the viewer, ts alone for the age-cutoff prune — mirroring
docker_events. Integration schema-shape test asserts columns + both indexes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CAGR73DUowdVFVvYzLXC5C

plugins/docker/models.py

@@ -163,6 +163,43 @@ class DockerEvent(Base):
     )
 
 
+class DockerLog(Base):
+    """Container log lines pushed by the host agent — one row per line.
+
+    Time-series, scoped to the reporting host (container names are only unique
+    within a host, same identity as docker_metrics). The agent tails each running
+    container incrementally and folds new lines into its metrics push; `ts` is the
+    line's own Docker timestamp. Bounded by a per-container size+age ring
+    (retention), so a chatty container just keeps a shorter window rather than
+    growing without limit.
+    """
+    __tablename__ = "docker_logs"
+
+    id: Mapped[str] = mapped_column(
+        String(36), primary_key=True, default=lambda: str(uuid.uuid4())
+    )
+    host_id: Mapped[str] = mapped_column(
+        String(36), ForeignKey("hosts.id", ondelete="CASCADE"), nullable=False, index=True
+    )
+    container_name: Mapped[str] = mapped_column(String(255), nullable=False, index=True)
+    ts: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False,
+        default=lambda: datetime.now(timezone.utc),
+    )
+    stream: Mapped[str] = mapped_column(String(8), nullable=False, default="stdout")
+    # stdout | stderr
+    line: Mapped[str] = mapped_column(Text, nullable=False, default="")
+
+    # Viewer filters on (host_id, container_name) and sorts by time; the ring
+    # prune walks the same key newest-first. A second index on `ts` alone serves
+    # the age-cutoff delete. Twin-index idiom, mirroring docker_events.
+    __table_args__ = (
+        Index("ix_docker_logs_host_container_time",
+              "host_id", "container_name", "ts"),
+        Index("ix_docker_logs_ts", "ts"),
+    )
+
+
 class DockerSwarmService(Base):
     """A Swarm service as seen by a manager host: desired vs running replicas.