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.

frontend/src/views/warranty/WarrantiesList.vue

@@ -51,7 +51,7 @@
                 <td>{{ w.enddate ? formatDate(w.enddate) : '-' }}</td>
                 <td>
                   <span v-if="!w.assets.length" class="muted">-</span>
-                  <router-link v-for="a in w.assets" :key="a.assetid" :to="assetLink(a)" class="asset-chip">{{ a.assetnumber }}</router-link>
+                  <router-link v-for="a in w.assets" :key="a.assetid" :to="assetLink(a)" class="asset-chip" :title="a.name || a.assetnumber">{{ a.assetnumber }}</router-link>
                 </td>
                 <td class="actions">
                   <button v-if="w.provider !== 'manual'" class="btn btn-secondary btn-sm" @click="refresh(w)">Refresh</button>
@@ -350,6 +350,9 @@ async function refresh(w) {
 .muted { color: var(--text-light); }
 .status-badge { padding: 0.15rem 0.6rem; border-radius: 12px; font-size: 0.78rem; font-weight: 600; }
 .filters { display: flex; align-items: center; gap: 1rem; flex-wrap: wrap; margin-bottom: 1rem; }
+/* Keep the "Status" label + its select on one line so it aligns with the
+   single-line search box next to it. */
+.filters label { display: inline-flex; align-items: center; gap: 0.4rem; }
 .filters .form-control { max-width: 320px; }
 .result-count { color: var(--text-light); font-size: 0.85rem; }
 .servicelevel-cell { max-width: 320px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }