feat: host inventory (agent.inventory), host detail page, UI columns

Store hardware/software snapshots on hosts; warn on hardware changes. Host card from Hosts list. Add agent version column to Events/Overview; rename Hosts table columns and sort by status.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/tests/test_telegram_templates.py

@@ -303,3 +303,26 @@ def test_ssh_failed_template():
     assert "root" in text
     assert "10.10.36.9" in text
     assert "3 / 5" in text
+
+
+def test_agent_inventory_hardware_change_template():
+    event = Event(
+        event_id="00000000-0000-4000-8000-000000000504",
+        host_id=1,
+        occurred_at=datetime(2026, 6, 4, 12, 0, tzinfo=timezone.utc),
+        category="agent",
+        type="agent.inventory",
+        severity="warning",
+        title="Hardware changed",
+        summary="memory_gb changed",
+        details={
+            "hardware_changes": [
+                {"field": "memory_gb", "old": 16.0, "new": 32.0},
+            ]
+        },
+        payload={},
+    )
+    text = format_event_telegram_html(event)
+    assert "железо" in text.lower() or "Изменилось" in text
+    assert "memory_gb" in text
+    assert "32" in text