test: фаза 4 — тесты extractors, ecosystem, i18n, metrics

- test_nexus.py: extract_pypi/go/npm, dispatch, edge cases (16 тестов)
- test_i18n.py: RU/EN переводы, fallback, форматирование, web UI (10 тестов)
- test_metrics.py: Prometheus endpoint (4 теста)
- test_webhooks.py: _detect_ecosystem (6 тестов), Go/npm webhook fixtures
- conftest.py: sample_nexus_go/npm_webhook fixtures
- Всего: 85 тестов (было 50)

tests/test_metrics.py

@@ -0,0 +1,35 @@
+"""Tests for Prometheus metrics endpoint."""
+
+import pytest
+
+
+@pytest.mark.asyncio
+async def test_metrics_returns_200(client):
+    resp = await client.get("/metrics")
+    assert resp.status_code == 200
+    assert "text/plain" in resp.headers["content-type"]
+
+
+@pytest.mark.asyncio
+async def test_metrics_contains_keys(client):
+    resp = await client.get("/metrics")
+    text = resp.text
+    assert "guarddog_scans_total" in text
+    assert "guarddog_scans_flagged_total" in text
+    assert "guarddog_findings_total" in text
+    assert "guarddog_scans_by_status" in text
+    assert "guarddog_scans_by_ecosystem" in text
+    # last_scan may not be present if no scans exist
+
+
+@pytest.mark.asyncio
+async def test_metrics_help_section(client):
+    resp = await client.get("/metrics")
+    assert "# HELP" in resp.text
+    assert "# TYPE" in resp.text
+
+
+@pytest.mark.asyncio
+async def test_metrics_last_scan_with_data(client, sample_flagged_scan):
+    resp = await client.get("/metrics")
+    assert "guarddog_last_scan_timestamp_seconds" in resp.text