fix(n8n): resolve duplicate key constraint on tag_entity during workflow import

n8n import:workflow --separate imports each JSON file independently. All 4
workflows shared the same tags (parapharmacy, scraper), so the second import
tried to INSERT duplicate tag names, hitting the unique index on
tag_entity.name.

- Remove tags field from all 4 workflow JSON files (cosmetic, re-add via UI)
- Add cleanup-db.js to wipe workflow data before import
- Add --overwrite flag to import command as safety net
- Add cleanup-db.js volume mount to n8n-init container

n8n/workflows/parapharmacy-all-sources.json

@@ -129,6 +129,5 @@
     }
   },
   "active": false,
-  "settings": { "executionOrder": "v1" },
-  "tags": [{ "name": "parapharmacy" }, { "name": "scraper" }, { "name": "scheduled" }]
+  "settings": { "executionOrder": "v1" }
 }