refactor: реструктуризация — core/, db/, routes/, web/

guarddog_nexus/
├── core/          scanner, harvester, nexus, llm
├── db/            engine, models, queries
├── routes/        webhooks, api_*, web
└── web/           templates + static

- 11 файлов перемещено (git mv — сохранена история)
- Все импорты обновлены (~15 файлов)
- main.py, tests — исправлены пути
- 50/50 тестов, ruff clean

tests/test_webhooks.py

@@ -34,7 +34,7 @@ async def test_webhook_ignores_created_action(client, sample_nexus_webhook):
 @pytest.mark.asyncio
 async def test_webhook_accepts_asset_updated(client, sample_nexus_webhook):
     sample_nexus_webhook["action"] = "UPDATED"
-    with patch("guarddog_nexus.webhooks._scan_in_background") as _mock:
+    with patch("guarddog_nexus.routes.webhooks._scan_in_background") as _mock:
         resp = await client.post("/webhooks/nexus", json=sample_nexus_webhook)
         assert resp.status_code == 200
         assert resp.json()["status"] == "accepted"
@@ -68,7 +68,7 @@ async def test_webhook_no_asset_or_component(client):
 
 @pytest.mark.asyncio
 async def test_webhook_accepts_component(client, sample_nexus_component_webhook):
-    with patch("guarddog_nexus.webhooks._scan_component") as _mock:
+    with patch("guarddog_nexus.routes.webhooks._scan_component") as _mock:
         resp = await client.post("/webhooks/nexus", json=sample_nexus_component_webhook)
         assert resp.status_code == 200
         data = resp.json()