Bulk Dell warranty sync + add-warranty from asset pages

- POST /warranty/sync/dell: auto-detect Dell hardware by service tag (asset
  serial) and create warranties for the ones Dell recognizes, in batches of 100.
  Only looks up assets that lack a dated warranty, so re-runs are cheap and
  non-Dell serials are filtered out by Dell. DellProvider.bulk_lookup batches
  tags over the cached token.
- "Sync Dell" button on the Warranties page with a toast summary.
- WarrantyPanel "Add one / Add-manage" links deep-link to the warranties add
  modal pre-linked to that asset (?addfor=); WarrantiesList opens it prefilled.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plugins/warranty/services/providers.py

@@ -203,6 +203,34 @@ class DellProvider(WarrantyProvider):
         token = self._get_token(config)
         return self._map(self._fetch(config, token, servicetag))
 
+    def bulk_lookup(self, servicetags):
+        """Look up many tags at once. Dell takes up to 100 tags per call.
+
+        Returns {SERVICETAG_UPPER: {servicelevel, startdate, enddate}} for tags
+        Dell recognizes; unknown/non-Dell tags are simply absent.
+        """
+        config = self._config()
+        if not (config['enabled'] and config['clientid'] and config['clientsecret']):
+            raise ProviderNotConfigured(
+                'Dell warranty lookup is not configured. Set warranty_dell_enabled, '
+                'clientid and clientsecret in Settings > Integrations.'
+            )
+        tags = [t.strip() for t in servicetags if t and t.strip()]
+        if not tags:
+            return {}
+        token = self._get_token(config)
+        results = {}
+        for start in range(0, len(tags), 100):
+            chunk = tags[start:start + 100]
+            payload = self._fetch(config, token, ','.join(chunk))
+            assets = payload if isinstance(payload, list) else [payload]
+            for asset in assets:
+                tag = (asset.get('serviceTag') or '').upper()
+                mapped = self._map([asset])
+                if tag and mapped:
+                    results[tag] = mapped
+        return results
+
 
 class ApiProvider(WarrantyProvider):
     """Generic config-shaped stub for vendors not yet wired (Lenovo, HP)."""