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-scraper.json

@@ -170,13 +170,5 @@
   "settings": {
     "executionOrder": "v1"
   },
-  "versionId": "1",
-  "tags": [
-    {
-      "name": "parapharmacy"
-    },
-    {
-      "name": "scraper"
-    }
-  ]
+  "versionId": "1"
 }