refactor(ui): CardHeading primitive for icon+title card/dialog headings (DRY pattern sweep)

The icon+title v-card-title heading (d-flex align-center + gap + <v-icon size=small> +
<span>) was hand-rolled identically in 13 cards/dialogs (15 heading instances).
Consolidate to <CardHeading icon title> (components/common) with an iconColor
prop (error headings) and a default slot for trailing content (spacer+actions,
inline status chip). Adopted everywhere the pattern appears — all-or-nothing per
the hardened DRY process.

Over-DRY guard: plain text-only <v-card-title> one-liners are NOT this pattern
and stay; DownloadDetailModal leads with a status CHIP (not an icon), a different
concept, left alone. §8b: the only remaining d-flex align-center v-card-title is
that intentional variant. Catalog updated.

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

frontend/src/components/common/CardHeading.vue

@@ -0,0 +1,25 @@
+<template>
+  <!-- Canonical card/dialog heading: an optional leading icon + the title, with
+       a default slot for trailing content (a v-spacer + actions, or an inline
+       status chip). The icon+title v-card-title row was hand-rolled identically
+       in 14 cards/dialogs (DRY pattern sweep 2026-06-09). Plain text-only
+       v-card-titles are NOT this pattern and keep using <v-card-title> directly. -->
+  <v-card-title class="d-flex align-center fc-card-heading">
+    <v-icon v-if="icon" :icon="icon" :color="iconColor || undefined" size="small" />
+    <span>{{ title }}</span>
+    <slot />
+  </v-card-title>
+</template>
+
+<script setup>
+defineProps({
+  icon: { type: String, default: '' },
+  title: { type: String, default: '' },
+  // e.g. 'error' for danger/error headings; '' keeps the default text color.
+  iconColor: { type: String, default: '' },
+})
+</script>
+
+<style scoped>
+.fc-card-heading { gap: 10px; }
+</style>