refactor(ui): consolidate 7 hand-rolled kebabs into one KebabMenu (DRY pattern sweep)

First pattern-consistency DRY pass (process #594). The overflow kebab was
hand-rolled 7 ways in two divergent activator strategies — Pattern A
(#activator + v-bind) which silently breaks inside the teleported image modal
(#711), and Pattern B (manual v-model + activator=parent + open-on-click=false +
z-index 2400) the modal kebabs needed as a workaround.

New <KebabMenu> (components/common) bakes in the modal-safe strategy
UNIVERSALLY, so every kebab works in modal and non-modal contexts — folding the
latent #711-class bug fix into all five Pattern-A sites. Menu items go in the
default slot; variations (size/variant/location/label/min-width) are props.

Adopted across all 7: TagChip, SuggestionItem, TagCard, SeriesView card,
SeriesManageView, BackupRunsTable, SourceActions. Exhaustiveness (§8b):
mdi-dots-vertical now lives only in KebabMenu. Labeled dropdowns / nav menus /
filter popovers are a different concept and left alone. Seeded the pattern
catalog so new code reuses the primitive. Test: KebabMenu renders slot items +
trigger label/glyph + presentational props.

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

frontend/src/components/discovery/TagCard.vue

@@ -46,34 +46,25 @@
         <v-chip size="x-small" label>{{ card.kind }}</v-chip>
         <div class="fc-tagcard__meta-right">
           <span class="fc-tagcard__count">{{ card.image_count }}</span>
-          <v-menu>
-            <template #activator="{ props: act }">
-              <v-btn
-                class="fc-tagcard__menu"
-                icon="mdi-dots-vertical" size="x-small" variant="text"
-                v-bind="act" @click.stop
-              />
-            </template>
-            <v-list density="compact">
-              <v-list-item
-                v-if="card.kind === 'character'"
-                title="Set fandom…"
-                prepend-icon="mdi-book-open-page-variant"
-                @click="$emit('set-fandom', card)"
-              />
-              <v-list-item
-                title="Merge with…"
-                prepend-icon="mdi-call-merge"
-                @click="$emit('merge-with', card)"
-              />
-              <v-list-item
-                title="Delete tag"
-                prepend-icon="mdi-delete"
-                base-color="error"
-                @click="$emit('delete', card)"
-              />
-            </v-list>
-          </v-menu>
+          <KebabMenu class="fc-tagcard__menu" :label="`Actions for ${card.name}`">
+            <v-list-item
+              v-if="card.kind === 'character'"
+              title="Set fandom…"
+              prepend-icon="mdi-book-open-page-variant"
+              @click="$emit('set-fandom', card)"
+            />
+            <v-list-item
+              title="Merge with…"
+              prepend-icon="mdi-call-merge"
+              @click="$emit('merge-with', card)"
+            />
+            <v-list-item
+              title="Delete tag"
+              prepend-icon="mdi-delete"
+              base-color="error"
+              @click="$emit('delete', card)"
+            />
+          </KebabMenu>
         </div>
       </div>
     </v-card-text>
@@ -82,6 +73,7 @@
 
 <script setup>
 import { ref } from 'vue'
+import KebabMenu from '../common/KebabMenu.vue'
 
 const props = defineProps({ card: { type: Object, required: true } })
 const emit = defineEmits([