Warranties: fix N+1 slowness, filter alignment, and Covers hover

- Perf: list_warranties did a db.session.get(Asset) per link per warranty
  (~1.8s for the full list). Eager-load the links and batch-fetch every linked
  asset in one query -> ~0.19s.
- Filters: the "Status" label wrapped its select onto a second line, so the
  dropdown sat above the search box; keep the label inline so they align.
- Covers: each asset chip now shows the asset name (often the hostname/alias) on
  hover, keeping the machine number as the label.

plugins/warranty/api/routes.py

@@ -9,6 +9,7 @@ from datetime import date, datetime, timezone
 
 from flask import Blueprint, request
 from flask_jwt_extended import jwt_required
+from sqlalchemy.orm import joinedload
 
 from shopdb.api import (
     db, Asset,
@@ -41,12 +42,15 @@ def _asset_summary(asset):
     }
 
 
-def _warranty_payload(warranty, today=None):
-    """to_dict plus the linked-asset summaries."""
+def _warranty_payload(warranty, today=None, assetmap=None):
+    """to_dict plus the linked-asset summaries. Pass assetmap (assetid -> Asset)
+    to avoid a per-link query when serializing a list; without it, falls back to
+    a per-link get (fine for a single warranty)."""
     data = warranty.to_dict(today)
     assets = []
     for link in warranty.links:
-        asset = db.session.get(Asset, link.assetid)
+        asset = assetmap.get(link.assetid) if assetmap is not None \
+            else db.session.get(Asset, link.assetid)
         if asset:
             assets.append(_asset_summary(asset))
     data['assets'] = assets
@@ -86,10 +90,17 @@ def list_warranties():
     if assetid:
         query = (query.join(WarrantyAsset, WarrantyAsset.warrantyid == Warranty.warrantyid)
                       .filter(WarrantyAsset.assetid == assetid))
-    warranties = query.order_by(Warranty.enddate.is_(None), Warranty.enddate).all()
+    warranties = (query.options(joinedload(Warranty.links))
+                  .order_by(Warranty.enddate.is_(None), Warranty.enddate).all())
+
+    # Batch-fetch every linked asset in ONE query (was N+1: a db.session.get per
+    # link per warranty, ~1.8s for the full list).
+    assetids = {link.assetid for w in warranties for link in w.links}
+    assetmap = ({a.assetid: a for a in Asset.query.filter(Asset.assetid.in_(assetids)).all()}
+                if assetids else {})
 
     today = date.today()
-    items = [_warranty_payload(w, today) for w in warranties]
+    items = [_warranty_payload(w, today, assetmap) for w in warranties]
 
     status_filter = request.args.get('status')
     if status_filter: