feat(deps): vuetify 3→4 (batch 4 phase B, #1449)

Vuetify 4 is a Material-Design-3 styling refresh with revert snippets, not a
component-API overhaul. FC's exposure was small:

- Bump vuetify ^4, vite-plugin-vuetify ^2.1.0, vue ^3.5, engines node>=24.
- Restore the dropped global CSS reset (minimal reset from the upgrade guide) in
  Vuetify's own low-precedence reset layer, so FC's margin-zeroing assumptions hold.
- v-row prop→utility: 'dense' → density=compact (×3), align=center → class=align-center.
- v-snackbar: multi-line removed → min-height=68.
- v-autocomplete #item slot: item→internalItem (item now aliases raw) in TagPicker
  + GalleryFilterBar (item.raw.* → internalItem.raw.*).

ACCEPTED (cosmetic, operator reviews live per plan #158): MD3 typography
(text-body-2 ×73), non-uppercase buttons (v4 dropped the uppercase default),
MD3 elevation. CI verifies BUILD only — the LOOK is the live-review pass.

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

frontend/package.json

@@ -4,7 +4,7 @@
   "private": true,
   "type": "module",
   "engines": {
-    "node": ">=22"
+    "node": ">=24"
   },
   "scripts": {
     "dev": "vite",
@@ -13,16 +13,16 @@
     "test:unit": "vitest run"
   },
   "dependencies": {
-    "vue": "^3.4.0",
+    "vue": "^3.5.0",
     "vue-router": "^5.0.0",
     "pinia": "^3.0.0",
-    "vuetify": "^3.5.0",
+    "vuetify": "^4.0.0",
     "@mdi/font": "^7.4.0"
   },
   "devDependencies": {
     "@vitejs/plugin-vue": "^6.0.0",
     "vite": "^8.0.0",
-    "vite-plugin-vuetify": "^2.0.0",
+    "vite-plugin-vuetify": "^2.1.0",
     "sass": "^1.71.0",
     "vitest": "^4.0.0",
     "@vue/test-utils": "^2.4.0",

frontend/src/components/AppSnackbar.vue

@@ -1,7 +1,7 @@
 <template>
   <v-snackbar
     v-model="show" :color="color" location="bottom right" timeout="4000"
-    multi-line elevation="4"
+    min-height="68" elevation="4"
   >
     {{ message }}
     <template #actions>

frontend/src/components/cleanup/MinDimensionCard.vue

@@ -10,7 +10,7 @@
       filter, applied retroactively to the existing library.
     </p>
 
-    <v-row dense>
+    <v-row density="compact">
       <v-col cols="6">
         <v-text-field
           v-model.number="minW" label="Min width (px)" type="number"

frontend/src/components/cleanup/SingleColorAuditCard.vue

@@ -13,7 +13,7 @@
       cadence as the transparency audit.
     </p>
 
-    <v-row dense>
+    <v-row density="compact">
       <v-col cols="6">
         <v-text-field
           v-model.number="threshold" label="Threshold (0–1)"

frontend/src/components/common/TagPicker.vue

@@ -14,10 +14,10 @@
     @update:search="onSearch"
     @update:model-value="onPick"
   >
-    <template #item="{ props: itemProps, item }">
-      <v-list-item v-bind="itemProps" :title="item.raw.name">
+    <template #item="{ props: itemProps, internalItem }">
+      <v-list-item v-bind="itemProps" :title="internalItem.raw.name">
         <template #subtitle>
-          {{ item.raw.fandom_name ? `character · ${item.raw.fandom_name}` : item.raw.kind }}
+          {{ internalItem.raw.fandom_name ? `character · ${internalItem.raw.fandom_name}` : internalItem.raw.kind }}
         </template>
       </v-list-item>
     </template>

frontend/src/components/gallery/GalleryFilterBar.vue

@@ -13,14 +13,14 @@
       @update:search="onSearch"
       @update:model-value="onPick"
     >
-      <template #item="{ props: itemProps, item }">
-        <v-list-item v-bind="itemProps" :title="item.raw.name">
+      <template #item="{ props: itemProps, internalItem }">
+        <v-list-item v-bind="itemProps" :title="internalItem.raw.name">
           <template #prepend>
-            <v-icon size="small">{{ iconFor(item.raw) }}</v-icon>
+            <v-icon size="small">{{ iconFor(internalItem.raw) }}</v-icon>
           </template>
           <template #subtitle>
-            {{ item.raw.kind === 'artist' ? 'artist'
-              : (item.raw.fandom_name ? `character · ${item.raw.fandom_name}` : item.raw.kind) }}
+            {{ internalItem.raw.kind === 'artist' ? 'artist'
+              : (internalItem.raw.fandom_name ? `character · ${internalItem.raw.fandom_name}` : internalItem.raw.kind) }}
           </template>
         </v-list-item>
       </template>

frontend/src/components/settings/ImportFiltersForm.vue

@@ -15,7 +15,7 @@
           being dropped as duplicates;</strong> raise it to collapse more
           look-alikes. Applies to new imports.
         </div>
-        <v-row align="center" no-gutters>
+        <v-row no-gutters class="align-center">
           <v-col cols="12" sm="9">
             <v-slider
               v-model="local.phash_threshold"

frontend/src/components/settings/SystemStatsCards.vue

@@ -1,5 +1,5 @@
 <template>
-  <v-row dense>
+  <v-row density="compact">
     <v-col v-for="card in cards" :key="card.label" cols="12" sm="6" md="4" lg="3" xl="2">
       <v-card class="fc-stat">
         <v-card-text>

frontend/src/styles/app.css

@@ -39,3 +39,13 @@
    deliberately not used here. `.fc-muted` is a custom class Vuetify never
    emits, so no specificity/reorder fight — no !important needed. */
 .fc-muted { color: rgb(var(--v-theme-on-surface-variant)); }
+
+/* Vuetify 4 dropped its global CSS reset (normalisation moved into each
+   component). FC's layouts assumed the reset zeroed margins on text elements, so
+   restore just that — the "minimal reset" from the v4 upgrade guide — inside
+   Vuetify's own reset layer, which is low precedence so component + app styles
+   still win over it. Batch-4 Vuetify 3→4 (#1449). */
+@layer vuetify-core.reset {
+  ul, ol, figure, details, summary { padding: 0; margin: 0; }
+  h1, h2, h3, h4, h5, h6, p { margin: 0; }
+}