fix(metrics): time-series rows get time-ordered ids, so an insert stops costing a disk read (#5149)

Measured on dev (385a579), agent posts cut to five samples still dropped:
flush=8.8s for 990 rows, 6.6s for 680, 8.4s for 1000 — about 110 rows/s,
~9 ms a row, with rules and evaluation near zero. One random read per
row fits a random uuid4 primary key whose index no longer fits in memory:
every new row lands on a random page of it. (Inferred from the rate; the
table and index sizes have not been read.)

- steward.core.ids.time_ordered_id: a UUIDv7-layout string (48-bit ms
  timestamp, then random), same 36-char shape as the stored uuid4 ids, so
  no migration. Python's uuid7() arrives in 3.14; the image runs 3.13.
- Used for plugin_metrics and its hourly rollup, monitor_results,
  audit_events, the docker metrics/hourly/events/logs tables, and the
  traefik and unifi time series.
- MAX_SAMPLES_PER_INGEST 5 → 2 (~400 rows) for now: it fits the agent's
  10 s even at the old rate, so hosts land data whichever way the new rate
  comes out. Raise it once the new rate is measured.

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

plugins/docker/models.py

@@ -1,6 +1,5 @@
 # plugins/docker/models.py
 from __future__ import annotations
-import uuid
 from datetime import datetime, timezone
 from sqlalchemy import (
     BigInteger, Boolean, DateTime, Float, ForeignKey, Index, Integer, String, Text,
@@ -8,6 +7,7 @@ from sqlalchemy import (
 )
 from sqlalchemy.orm import Mapped, mapped_column
 from steward.models.base import Base
+from steward.core.ids import time_ordered_id
 
 
 class DockerContainer(Base):
@@ -67,7 +67,7 @@ class DockerMetric(Base):
     __tablename__ = "docker_metrics"
 
     id: Mapped[str] = mapped_column(
-        String(36), primary_key=True, default=lambda: str(uuid.uuid4())
+        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
@@ -103,7 +103,7 @@ class DockerMetricHourly(Base):
     __tablename__ = "docker_metrics_hourly"
 
     id: Mapped[str] = mapped_column(
-        String(36), primary_key=True, default=lambda: str(uuid.uuid4())
+        String(36), primary_key=True, default=time_ordered_id
     )
     host_id: Mapped[str] = mapped_column(
         String(36), ForeignKey("hosts.id", ondelete="CASCADE"), nullable=False
@@ -139,7 +139,7 @@ class DockerEvent(Base):
     __tablename__ = "docker_events"
 
     id: Mapped[str] = mapped_column(
-        String(36), primary_key=True, default=lambda: str(uuid.uuid4())
+        String(36), primary_key=True, default=time_ordered_id
     )
     host_id: Mapped[str] = mapped_column(
         String(36), ForeignKey("hosts.id", ondelete="CASCADE"), nullable=False
@@ -176,7 +176,7 @@ class DockerLog(Base):
     __tablename__ = "docker_logs"
 
     id: Mapped[str] = mapped_column(
-        String(36), primary_key=True, default=lambda: str(uuid.uuid4())
+        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