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_cli.py

@@ -2022,6 +2022,77 @@ class TestSnapshotCommand:
         assert result.exit_code == 0, result.output
         assert updater.call_args.kwargs["with_grafana_schema"] is False
 
+    def test_snapshot_with_publish_copy(
+        self,
+        tmp_path: Path,
+        mocker: MockerFixture,
+    ) -> None:
+        """--publish-copy calls publish_grafana_copy after update_observability."""
+        mocker.patch("mt5cli.cli.sdk.update_observability_with_config")
+        mock_publish = mocker.patch("mt5cli.grafana.publish_grafana_copy")
+        copy_path = tmp_path / "grafana.db"
+        result = runner.invoke(
+            app,
+            [
+                "-o",
+                str(tmp_path / "out.db"),
+                "snapshot",
+                "--publish-copy",
+                str(copy_path),
+            ],
+        )
+        assert result.exit_code == 0, result.output
+        mock_publish.assert_called_once()
+
+    def test_snapshot_no_publish_copy_by_default(
+        self,
+        tmp_path: Path,
+        mocker: MockerFixture,
+    ) -> None:
+        """Snapshot does not call publish_grafana_copy without --publish-copy."""
+        mocker.patch("mt5cli.cli.sdk.update_observability_with_config")
+        mock_publish = mocker.patch("mt5cli.grafana.publish_grafana_copy")
+        result = runner.invoke(app, ["-o", str(tmp_path / "out.db"), "snapshot"])
+        assert result.exit_code == 0, result.output
+        mock_publish.assert_not_called()
+
+
+class TestGrafanaSchemaPublishCopy:
+    """Tests for grafana-schema --publish-copy option."""
+
+    def test_grafana_schema_with_publish_copy(
+        self,
+        tmp_path: Path,
+        mocker: MockerFixture,
+    ) -> None:
+        """grafana-schema --publish-copy calls publish_grafana_copy."""
+        mock_publish = mocker.patch("mt5cli.grafana.publish_grafana_copy")
+        output = tmp_path / "out.db"
+        copy_path = tmp_path / "grafana.db"
+        result = runner.invoke(
+            app,
+            [
+                "-o",
+                str(output),
+                "grafana-schema",
+                "--publish-copy",
+                str(copy_path),
+            ],
+        )
+        assert result.exit_code == 0, result.output
+        mock_publish.assert_called_once()
+
+    def test_grafana_schema_no_publish_copy_by_default(
+        self,
+        tmp_path: Path,
+        mocker: MockerFixture,
+    ) -> None:
+        """grafana-schema does not call publish_grafana_copy by default."""
+        mock_publish = mocker.patch("mt5cli.grafana.publish_grafana_copy")
+        result = runner.invoke(app, ["-o", str(tmp_path / "out.db"), "grafana-schema"])
+        assert result.exit_code == 0, result.output
+        mock_publish.assert_not_called()
+
 
 class TestMain:
     """Tests for the main entry point."""