feat: Grafana copy publishing, dashboard examples, and optional OTel metrics

Implements three observability improvements:

#82 — publish_grafana_copy(): Uses SQLite online backup API (WAL-safe) to
atomically publish a consistent read-only copy beside the target. Adds
--publish-copy option to grafana-schema and snapshot CLI commands.

#83 — examples/grafana/: Minimal working Grafana setup with docker-compose,
provisioning datasource/dashboard YAML, and three dashboard JSON files
(mt5cli-overview, mt5cli-trades, mt5cli-market). All queries use grafana_*
views; no credentials or private paths included.

#84 — mt5cli/telemetry.py: Optional OTel metrics behind mt5cli[otel] extra.
Base install is unaffected. Adds _Mt5Metrics singleton (no-op until
configure_metrics() is called), wraps update_history() and
update_observability() with record_history_update / record_snapshot_update
context managers, and emits account/position gauges from snapshots.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_sdk.py

@@ -3120,3 +3120,62 @@ class TestUpdateObservability:
         call_kwargs = spy.call_args.kwargs
         assert call_kwargs["symbols"] == ["EURUSD"]
         assert call_kwargs["include_account"] is False
+
+    def test_update_observability_invokes_snapshot_telemetry(
+        self,
+        mock_client: MagicMock,
+        mocker: MockerFixture,
+        tmp_path: Path,
+    ) -> None:
+        """update_observability calls record_snapshot_update on the global metrics."""
+        mock_metrics = MagicMock()
+        mock_cm = MagicMock()
+        mock_cm.__enter__ = MagicMock(return_value=None)
+        mock_cm.__exit__ = MagicMock(return_value=False)
+        mock_metrics.record_snapshot_update.return_value = mock_cm
+        mocker.patch("mt5cli.sdk.get_metrics", return_value=mock_metrics)
+        update_observability(client=mock_client, output=tmp_path / "obs.db")
+        mock_metrics.record_snapshot_update.assert_called_once()
+
+    def test_update_observability_emits_account_metrics(
+        self,
+        mock_client: MagicMock,
+        mocker: MockerFixture,
+        tmp_path: Path,
+    ) -> None:
+        """_snapshot_account emits account gauges via get_metrics."""
+        mock_metrics = MagicMock()
+        mock_cm = MagicMock()
+        mock_cm.__enter__ = MagicMock(return_value=None)
+        mock_cm.__exit__ = MagicMock(return_value=False)
+        mock_metrics.record_snapshot_update.return_value = mock_cm
+        mocker.patch("mt5cli.sdk.get_metrics", return_value=mock_metrics)
+        update_observability(client=mock_client, output=tmp_path / "obs.db")
+        mock_metrics.record_account_state.assert_called_once()
+
+
+class TestUpdateHistoryTelemetry:
+    """Tests for telemetry hooks in update_history."""
+
+    def test_update_history_invokes_history_telemetry(
+        self,
+        mocker: MockerFixture,
+        tmp_path: Path,
+    ) -> None:
+        """update_history wraps write_incremental_datasets with telemetry."""
+        mock_client = MagicMock()
+        mock_client.copy_rates_range_as_df.return_value = pd.DataFrame()
+        mock_client.history_orders_get_as_df.return_value = pd.DataFrame()
+        mock_client.history_deals_get_as_df.return_value = pd.DataFrame()
+        mock_metrics = MagicMock()
+        mock_cm = MagicMock()
+        mock_cm.__enter__ = MagicMock(return_value=None)
+        mock_cm.__exit__ = MagicMock(return_value=False)
+        mock_metrics.record_history_update.return_value = mock_cm
+        mocker.patch("mt5cli.sdk.get_metrics", return_value=mock_metrics)
+        update_history(
+            client=mock_client,
+            output=tmp_path / "hist.db",
+            symbols=["EURUSD"],
+        )
+        mock_metrics.record_history_update.assert_called_once_with(dataset="history")