refactor(ui): SampleNameGrid primitive for maintenance-card previews (DRY pattern sweep)

The preview sample-name grid (scrollable monospace chip grid) was hand-rolled
5 times with verbatim-duplicated markup + CSS — TagMaintenanceCard (×4) and
PostMaintenanceCard. Consolidate to <SampleNameGrid> (components/common): pass
:names for the plain case, default slot for the normalize from→to chips
(styled via :slotted .fc-name). Removed the duplicated .fc-name-grid/.fc-name
CSS from both cards.

Over-DRY guard: only the verbatim-duplicated grid is merged — each card's
preview/commit logic and result-count lines genuinely differ and stay put;
MinDimensionCard's typed-token confirm is a separate variant, untouched.
§8b: fc-name-grid now lives only in SampleNameGrid. Catalog updated.

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

frontend/src/components/common/SampleNameGrid.vue

@@ -0,0 +1,32 @@
+<template>
+  <!-- Scrollable grid of monospace name chips — the preview "here's a sample of
+       what will change" surface shared by the maintenance cards (DRY pattern
+       sweep 2026-06-09). Pass `names` for the common case; use the default slot
+       to render custom chips (style them `.fc-name` and they inherit the look
+       via :slotted). The caller keeps its own v-if for the empty case. -->
+  <div class="fc-name-grid">
+    <slot>
+      <span v-for="(n, i) in names" :key="i" class="fc-name">{{ n }}</span>
+    </slot>
+  </div>
+</template>
+
+<script setup>
+defineProps({
+  names: { type: Array, default: () => [] },
+})
+</script>
+
+<style scoped>
+.fc-name-grid {
+  display: flex; flex-wrap: wrap; gap: 4px 8px;
+  max-height: 200px; overflow-y: auto;
+  padding: 8px; border-radius: 4px;
+  background: rgb(var(--v-theme-surface-light));
+}
+.fc-name, :slotted(.fc-name) {
+  font-family: 'JetBrains Mono', monospace;
+  font-size: 12px;
+  color: rgb(var(--v-theme-on-surface-variant));
+}
+</style>