warranty: fix bulk Dell re-check duplicating non-dell warranties

The bulk /sync/dell reuse check only matched an existing warranty when its
provider was exactly 'dell'. Warranties added by hand or via import default to
provider 'manual', so re-check-all did not recognize them and created a brand
new Dell warranty for every asset - duplicating the whole set.

Broaden the reuse match to treat a warranty as Dell by any signal (provider,
matching service tag, or a 'Dell' vendor), and canonicalize the reused row to
provider 'dell' so later re-checks match by provider and never duplicate.

plugins/warranty/api/routes.py

@@ -286,10 +286,22 @@ def sync_dell():
             existing = None
             for link in WarrantyAsset.query.filter_by(assetid=assetid).all():
                 candidate = db.session.get(Warranty, link.warrantyid)
-                if candidate and candidate.provider == 'dell':
+                # Reuse a warranty that is Dell by ANY signal, not just
+                # provider: a manually-added or imported Dell warranty carries
+                # provider 'manual' (create default) but the same service tag or
+                # a "Dell" vendor. Matching only provider=='dell' made re-check
+                # duplicate every one of those instead of updating it.
+                if candidate and (
+                        candidate.provider == 'dell'
+                        or (candidate.servicetag or '').strip().upper() == tag
+                        or (candidate.vendor or '').strip().lower() == 'dell'):
                     existing = candidate
                     break
             if existing:
+                # Canonicalize to Dell so later re-checks match by provider and
+                # never fall through to a duplicate.
+                existing.provider = 'dell'
+                existing.vendor = existing.vendor or 'Dell'
                 existing.servicelevel = found.get('servicelevel')
                 existing.startdate = _parse_date(found.get('startdate'))
                 existing.enddate = _parse_date(found.get('enddate'))