refactor(docker): container CPU and memory live in the one metric store (#5752)

#5752 "Container CPU and memory history lives in the one metric store;
docker_metrics and docker_metrics_hourly are retired". Container cpu_pct and
mem_pct already went to plugin_metrics for alerting; now mem_usage_bytes does
too, and every snapshot in an ingest (backlog included) is recorded at its
own time. The container history chart, Busiest Containers, a service's
history and the MCP container tools read plugin_metrics under resource
"<host>/<container>", rolled up and pruned by the shared metric retention.

docker_012_drop_metrics drops both tables. Their history is not copied
(lesson #5221 "A data migration's cost is set by the live table"); the
store already holds 7 days of container CPU and memory %. Docker retention
now prunes only lifecycle events, and Settings -> Thresholds has one
"Metric retention" card for every source.

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

plugins/docker/models.py

@@ -3,7 +3,6 @@ from __future__ import annotations
 from datetime import datetime, timezone
 from sqlalchemy import (
     BigInteger, Boolean, DateTime, Float, ForeignKey, Index, Integer, String, Text,
-    UniqueConstraint,
 )
 from sqlalchemy.orm import Mapped, mapped_column
 from steward.models.base import Base
@@ -61,69 +60,6 @@ class DockerContainer(Base):
     blk_write_bytes: Mapped[int | None] = mapped_column(BigInteger, nullable=True)
 
 
-class DockerMetric(Base):
-    """Time-series CPU/memory per container — one row per sample per running
-    container, scoped to the reporting host."""
-    __tablename__ = "docker_metrics"
-
-    id: Mapped[str] = mapped_column(
-        String(36), primary_key=True, default=time_ordered_id
-    )
-    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)
-    scraped_at: Mapped[datetime] = mapped_column(
-        DateTime(timezone=True), nullable=False,
-        default=lambda: datetime.now(timezone.utc),
-        index=True,
-    )
-    cpu_pct: Mapped[float] = mapped_column(Float, nullable=False, default=0.0)
-    mem_pct: Mapped[float] = mapped_column(Float, nullable=False, default=0.0)
-    # BigInteger: per-container memory usage exceeds 2^31 bytes (~2.1 GB) routinely.
-    mem_usage_bytes: Mapped[int] = mapped_column(BigInteger, nullable=False, default=0)
-
-    # Per-container history lookups filter on (host_id, container_name) then sort
-    # by time — a composite index keeps the rows() sparkline queries cheap.
-    __table_args__ = (
-        Index("ix_docker_metrics_host_container_time",
-              "host_id", "container_name", "scraped_at"),
-    )
-
-
-class DockerMetricHourly(Base):
-    """Hourly rollup of docker_metrics — avg cpu/mem per container per hour.
-
-    Raw per-sample rows (~2880/container/day at 30s) are pruned beyond a short
-    window; before deletion they're aggregated here so multi-day history stays
-    cheap to store and query. One row per (host, container, hour bucket); the
-    unique constraint lets retention upsert idempotently if it re-runs before the
-    raw rows are deleted. `bucket` is the hour-truncated sample time.
-    """
-    __tablename__ = "docker_metrics_hourly"
-
-    id: Mapped[str] = mapped_column(
-        String(36), primary_key=True, default=time_ordered_id
-    )
-    host_id: Mapped[str] = mapped_column(
-        String(36), ForeignKey("hosts.id", ondelete="CASCADE"), nullable=False
-    )
-    container_name: Mapped[str] = mapped_column(String(255), nullable=False)
-    bucket: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False)
-    cpu_pct: Mapped[float] = mapped_column(Float, nullable=False, default=0.0)
-    mem_pct: Mapped[float] = mapped_column(Float, nullable=False, default=0.0)
-    mem_usage_bytes: Mapped[int] = mapped_column(BigInteger, nullable=False, default=0)
-    sample_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
-
-    __table_args__ = (
-        # One bucket per container per host — the conflict target for the
-        # idempotent rollup upsert; doubles as the history-query index.
-        UniqueConstraint("host_id", "container_name", "bucket",
-                         name="uq_docker_metrics_hourly_bucket"),
-        Index("ix_docker_metrics_hourly_bucket", "bucket"),
-    )
-
-
 class DockerEvent(Base):
     """Lifecycle events derived by diffing consecutive host snapshots.
 
@@ -167,7 +103,7 @@ 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
+    within a host, same identity as docker_containers). 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