feat(host_agent): agent reports its primary IP; mirror into Host.address (task 274)

The agent now detects its own primary non-loopback IP (UDP-socket trick, no
packets sent) and sends it in the metadata bag; bumps AGENT_VERSION 1.0.0->1.1.0
and re-detects on SIGHUP. The server persists it on HostAgentRegistration.host_ip
and mirrors it into Host.address ONLY when that field is blank — an admin-typed
address is never overwritten. The reported IP shows in the settings table so
admins can see drift regardless.

- agent.py: detect_primary_ip(); host_ip in collect_metadata(); refresh on reload
- routes.py: pure pick_host_address() helper; ingest persists host_ip + mirrors
- models.py + migration host_agent_002_host_ip: new String(45) column
- settings_list.html: Reported IP column
- plugin.yaml: 1.0.0 -> 1.1.0
- tests: pick_host_address (fill-when-blank / never-clobber / no-op),
  detect_primary_ip (never raises, non-loopback), metadata carries host_ip

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/plugins/host_agent/test_host_ip.py

@@ -0,0 +1,41 @@
+"""Tests for agent-reported primary IP (task 274)."""
+from plugins.host_agent.routes import pick_host_address
+from plugins.host_agent import agent as a
+
+
+# ── pick_host_address: fill only when blank, never clobber ────────────────────
+
+def test_pick_fills_when_current_blank():
+    assert pick_host_address("", "10.0.0.5") == "10.0.0.5"
+    assert pick_host_address(None, "10.0.0.5") == "10.0.0.5"
+    assert pick_host_address("   ", "10.0.0.5") == "10.0.0.5"
+
+
+def test_pick_keeps_admin_value():
+    # A non-blank current address is never overwritten.
+    assert pick_host_address("monitor.example.com", "10.0.0.5") is None
+    assert pick_host_address("192.168.1.9", "10.0.0.5") is None
+
+
+def test_pick_no_reported_ip_is_noop():
+    assert pick_host_address("", None) is None
+    assert pick_host_address("", "") is None
+    assert pick_host_address(None, None) is None
+
+
+# ── detect_primary_ip: never raises; None or a non-loopback string ────────────
+
+def test_detect_primary_ip_never_raises_and_is_sane():
+    ip = a.detect_primary_ip()
+    assert ip is None or isinstance(ip, str)
+    if ip is not None:
+        assert not ip.startswith("127.")
+        assert ip  # non-empty
+
+
+# ── host_ip rides in the metadata bag the agent sends ─────────────────────────
+
+def test_collect_metadata_includes_host_ip_key():
+    md = a.collect_metadata()
+    assert "host_ip" in md  # present even if None when offline
+    assert set(md) >= {"kernel", "distro", "arch", "host_ip"}