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/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>