feat(docker): per-container enrichment — health, restarts, exit code, I/O, grouping

First slice of milestone 77 (Docker monitoring depth). Surfaces real per-container
stats beyond basic state, all read-only on the existing push model.

- agent (→1.4.0): collect_docker now inspects each container (health, restart
  count, exit code, OOM) and reads net + block I/O from the stats payload; pulls
  compose project + swarm service/task/node from container labels. Per-container
  inspect+stats calls run over a small bounded ThreadPool so the ~1s-per-stats
  blocking doesn't stretch the sample on a busy host.
- schema (docker_003): additive columns on docker_containers — health, exit_code,
  oom_killed, compose_project, service_name, task_id, node_id, and BigInteger
  net/blk byte counters.
- ingest: persists the enrichment + restart_count (.get keeps older agents working).
- ui: Docker page rows now show health badge, uptime ("up 3d 4h"), restart count,
  exit code (+OOM) for stopped containers, and compose/service grouping label.
- tests: agent helpers (grouping, inspect fields, net/IO sum) + collect_docker
  assembly incl. inspect; integration asserts enrichment round-trips.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016Jg27rgypiW2efULXJDtMC

tests/integration/test_docker.py

@@ -75,6 +75,11 @@ def test_persist_scopes_containers_by_host(app):
         "name": "web", "container_id": "abc123", "image": "nginx",
         "status": "running", "cpu_pct": 12.5, "mem_pct": 30.0,
         "mem_usage_bytes": 100, "mem_limit_bytes": 200, "ports": [], "started_at": None,
+        # enrichment (agent ≥ 1.4.0)
+        "health": "healthy", "restart_count": 2, "exit_code": 0, "oom_killed": False,
+        "compose_project": "stack", "service_name": "web",
+        "net_rx_bytes": 1000, "net_tx_bytes": 2000,
+        "blk_read_bytes": 4096, "blk_write_bytes": 8192,
     }])]
 
     async def _go():
@@ -101,9 +106,14 @@ def test_persist_scopes_containers_by_host(app):
             resources = {r[0] for r in (await s.execute(text(
                 "SELECT DISTINCT resource_name FROM plugin_metrics "
                 "WHERE source_module = 'docker'"))).all()}
-            return web_rows, metric_hosts, resources
+            # Enrichment columns persisted (check one host's row).
+            enrich = (await s.execute(text(
+                "SELECT health, restart_count, service_name, net_rx_bytes "
+                "FROM docker_containers WHERE name = 'web' LIMIT 1"))).first()
+            return web_rows, metric_hosts, resources, enrich
 
-    web_rows, metric_hosts, resources = asyncio.run(_go())
+    web_rows, metric_hosts, resources, enrich = asyncio.run(_go())
     assert web_rows == 2          # one 'web' per host, keyed by (host_id, name)
     assert metric_hosts == 2      # time-series rows scoped per host
     assert resources == {"alpha/web", "beta/web"}
+    assert enrich == ("healthy", 2, "web", 1000)   # enrichment round-trips